segfault during vbucketmigrator restart

Set up a master/replica configuration using vbucketmigrator
Load 200k keys into master and wait for replication
kill (-9) vbucketmigrator and restart it 100 times

Thread 9 (process 6391):
#0 0x00002aaaabaa3018 in epoll_wait () from /lib64/libc.so.6
#1 0x00002aaaaaef4c25 in epoll_dispatch () from /opt/membase/lib/libevent-2.0.so.2
#2 0x00002aaaaaedb58b in event_base_loop () from /opt/membase/lib/libevent-2.0.so.2
#3 0x0000000000417824 in main ()

Thread 8 (process 6402):
#0 0x00002aaaab7bdf70 in pthread_cond_timedwait@@GLIBC_2.3.2 () from /lib64/libpthread.so.0
#1 0x00002aaaabe37d68 in SyncObject::wait (this=0x67c240, tv=@0x67d5c8) at syncobject.hh:42
#2 0x00002aaaabe342bd in IdleTask::run (this=0x67d5c0, d=@0x67c230) at dispatcher.cc:244
#3 0x00002aaaabe353b8 in Dispatcher::run (this=0x67c230) at dispatcher.cc:119
#4 0x00002aaaabe35918 in launch_dispatcher_thread (arg=0x67c230) at dispatcher.cc:28
#5 0x00002aaaab7b9617 in start_thread () from /lib64/libpthread.so.0
#6 0x00002aaaabaa2c2d in clone () from /lib64/libc.so.6

Thread 7 (process 6403):
#0 0x00002aaaab7bdf70 in pthread_cond_timedwait@@GLIBC_2.3.2 () from /lib64/libpthread.so.0
#1 0x00002aaaabe37d68 in SyncObject::wait (this=0x67d680, tv=@0x67e8b8) at syncobject.hh:42
#2 0x00002aaaabe342bd in IdleTask::run (this=0x67e8b0, d=@0x67d670) at dispatcher.cc:244
#3 0x00002aaaabe353b8 in Dispatcher::run (this=0x67d670) at dispatcher.cc:119
#4 0x00002aaaabe35918 in launch_dispatcher_thread (arg=0x67d670) at dispatcher.cc:28
#5 0x00002aaaab7b9617 in start_thread () from /lib64/libpthread.so.0
#6 0x00002aaaabaa2c2d in clone () from /lib64/libc.so.6

Thread 6 (process 6409):
#0 0x00002aaaabaa3018 in epoll_wait () from /lib64/libc.so.6
#1 0x00002aaaaaef4c25 in epoll_dispatch () from /opt/membase/lib/libevent-2.0.so.2
#2 0x00002aaaaaedb58b in event_base_loop () from /opt/membase/lib/libevent-2.0.so.2
#3 0x00000000004185d4 in worker_libevent ()
#4 0x00002aaaab7b9617 in start_thread () from /lib64/libpthread.so.0
#5 0x00002aaaabaa2c2d in clone () from /lib64/libc.so.6

Thread 5 (process 6410):
#0 0x00002aaaabaa3018 in epoll_wait () from /lib64/libc.so.6
#1 0x00002aaaaaef4c25 in epoll_dispatch () from /opt/membase/lib/libevent-2.0.so.2
#2 0x00002aaaaaedb58b in event_base_loop () from /opt/membase/lib/libevent-2.0.so.2
#3 0x00000000004185d4 in worker_libevent ()
#4 0x00002aaaab7b9617 in start_thread () from /lib64/libpthread.so.0
#5 0x00002aaaabaa2c2d in clone () from /lib64/libc.so.6

Thread 4 (process 6411):
#0 0x00002aaaabaa3018 in epoll_wait () from /lib64/libc.so.6
#1 0x00002aaaaaef4c25 in epoll_dispatch () from /opt/membase/lib/libevent-2.0.so.2
#2 0x00002aaaaaedb58b in event_base_loop () from /opt/membase/lib/libevent-2.0.so.2
#3 0x00000000004185d4 in worker_libevent ()
#4 0x00002aaaab7b9617 in start_thread () from /lib64/libpthread.so.0
#5 0x00002aaaabaa2c2d in clone () from /lib64/libc.so.6

Thread 3 (process 6412):
#0 0x00002aaaabaa3018 in epoll_wait () from /lib64/libc.so.6
#1 0x00002aaaaaef4c25 in epoll_dispatch () from /opt/membase/lib/libevent-2.0.so.2
#2 0x00002aaaaaedb58b in event_base_loop () from /opt/membase/lib/libevent-2.0.so.2
#3 0x00000000004185d4 in worker_libevent ()
#4 0x00002aaaab7b9617 in start_thread () from /lib64/libpthread.so.0
#5 0x00002aaaabaa2c2d in clone () from /lib64/libc.so.6

Thread 2 (process 6413):
#0 0x00002aaaab7c02e4 in __lll_lock_wait () from /lib64/libpthread.so.0
#1 0x00002aaaab7bbc3a in _L_lock_1034 () from /lib64/libpthread.so.0
#2 0x00002aaaab7bbafc in pthread_mutex_lock () from /lib64/libpthread.so.0
#3 0x00000000004048c7 in conn_close ()
#4 0x0000000000419260 in libevent_tap_process ()
#5 0x00002aaaaaedae3f in event_persist_closure () from /opt/membase/lib/libevent-2.0.so.2
#6 0x00002aaaaaedaa31 in event_process_active_single_queue () from /opt/membase/lib/libevent-2.0.so.2
#7 0x00002aaaaaedaffb in event_process_active () from /opt/membase/lib/libevent-2.0.so.2
#8 0x00002aaaaaedb5d3 in event_base_loop () from /opt/membase/lib/libevent-2.0.so.2
#9 0x00000000004185d4 in worker_libevent ()
#10 0x00002aaaab7b9617 in start_thread () from /lib64/libpthread.so.0
#11 0x00002aaaabaa2c2d in clone () from /lib64/libc.so.6

Thread 1 (process 6404):
#0 0x00000000004194d3 in notify_io_complete ()
#1 0x00002aaaabe4ccb0 in EventuallyPersistentEngine::notifyIOComplete (this=0x643b50, cookie=0x2aaab6224208, status=ENGINE_DISCONNECT) at ep_engine.h:397
#2 0x00002aaaabeadd2e in TapConnectionReaperCallback (this=0x2aaab84eb1c0, e=@0x643b50, c=0x3012cf0) at tapconnmap.cc:24
#3 0x00002aaaabeab674 in TapConnMap::notifyIOThreadMain (this=0x6440f0) at tapconnmap.cc:433
#4 0x00002aaaabe59bfa in EventuallyPersistentEngine::notifyTapIoThread (this=0x643b50) at ep_engine.cc:3498
#5 0x00002aaaabe5f140 in EvpNotifyTapIo (arg=0x643b50) at ep_engine.cc:862
#6 0x00002aaaab7b9617 in start_thread () from /lib64/libpthread.so.0
#7 0x00002aaaabaa2c2d in clone () from /lib64/libc.so.6