MagmaKVStore::makeCompactionContext: Have not set makeCompactionContextCallback to create a compaction_ctx

* Had a four node cluster

* Created 7 million docs(of size 2048 bytes)

* Updated all 7 million docs such that docs moves from seq Tree to key Tree

* Repeate the above step twice

* Observed Magma crashed with MagmaKVStore::makeCompactionContext(Vbid)

./testrunner -i /tmp/testexec.95080.ini bucket_storage=magma,GROUP=P0;SET2,bucket_eviction_policy=fullEviction,randomize_value=True,rerun=false,disable_magma_commit_points=True,fragmentation=50,replicas=0,test_itr=2,get-cbcollect-info=True,infra_log_level=critical,log_level=error -t magma.magma_basic_crud.BasicCrudTests.test_move_val_btwn_key_and_seq_trees,num_items=7000000,nodes_init=4,sdk_timeout=60,vbuckets=128,randomize_doc_size=True,GROUP=P0;SET2

(gdb) bt

#0  0x00007fac481ca337 in raise () from /lib64/libc.so.6

#1  0x00007fac481cba28 in abort () from /lib64/libc.so.6

#2  0x00007fac48d28195 in __gnu_cxx::__verbose_terminate_handler() () from /opt/couchbase/bin/../lib/libstdc++.so.6

#3  0x000000000054a9f2 in backtrace_terminate_handler() ()

#4  0x00007fac48d25f86 in __cxxabiv1::__terminate(void (*)()) () from /opt/couchbase/bin/../lib/libstdc++.so.6

#5  0x00007fac48d25fd1 in std::terminate() () from /opt/couchbase/bin/../lib/libstdc++.so.6

#6  0x00007fac48d26213 in __cxa_throw () from /opt/couchbase/bin/../lib/libstdc++.so.6

#7  0x00007fac4c5fabcf in MagmaKVStore::makeCompactionContext(Vbid) () from /opt/couchbase/bin/../lib/libep.so

#8  0x00007fac4c5fb446 in MagmaKVStore::compactionCallBack(MagmaKVStore::MagmaCompactionCB&, magma::Slice const&, magma::Slice const&, magma::Slice const&) ()

   from /opt/couchbase/bin/../lib/libep.so

#9  0x00007fac4bee6c8a in magma::DocSeqGCContext::Transform(magma::Slice const&, magma::Slice const&, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >&, magma::Slice*) () from /opt/couchbase/bin/../lib/libmagma.so

#10 0x00007fac4be9eb7e in magma::ItemGCFilter::Process(std::vector<std::pair<magma::Slice, magma::Slice>, std::allocator<std::pair<magma::Slice, magma::Slice> > >&, std::vector<std::pair<magma::Slice, magma::Slice>, std::allocator<std::pair<magma::Slice, magma::Slice> > >*) () from /opt/couchbase/bin/../lib/libmagma.so

#11 0x00007fac4bef6960 in magma::LSMTree::mergeSSTables(std::vector<std::shared_ptr<magma::Table>, std::allocator<std::shared_ptr<magma::Table> > >&, magma::ItemGCFilter&, unsigned long, double, std::vector<std::shared_ptr<magma::Table>, std::allocator<std::shared_ptr<magma::Table> > >*) ()

   from /opt/couchbase/bin/../lib/libmagma.so

#12 0x00007fac4be97ac6 in magma::LSMTree::compactLevelForInputs(int, int, std::unique_lock<std::mutex>&, std::vector<std::shared_ptr<magma::Table>, std::allocator<std::shared_ptr<magma::Table> > >&, std::vector<std::shared_ptr<magma::Table>, std::allocator<std::shared_ptr<magma::Table> > >&, bool, std::function<std::unique_ptr<magma::GCContext, std::default_delete<magma::GCContext> > (bool)>) () from /opt/couchbase/bin/../lib/libmagma.so

#13 0x00007fac4be98eed in magma::LSMTree::compactLevel(int, std::unique_lock<std::mutex>&, bool, std::function<std::unique_ptr<magma::GCContext, std::default_delete<magma::GCContext> > (bool)>) () from /opt/couchbase/bin/../lib/libmagma.so

#14 0x00007fac4be9a2e6 in magma::LSMTree::compact(std::unique_lock<std::mutex>&) () from /opt/couchbase/bin/../lib/libmagma.so

#15 0x00007fac4beee367 in std::_Function_handler<void (), magma::LSMTree::queueCompaction()::{lambda()#1}>::_M_invoke(std::_Any_data const&) ()

   from /opt/couchbase/bin/../lib/libmagma.so

#16 0x00007fac4bf3dd39 in magma::TaskWorker::loop(void*) () from /opt/couchbase/bin/../lib/libmagma.so

#17 0x00007fac4af2c777 in platform_thread_wrap(void*) () from /opt/couchbase/bin/../lib/libplatform_so.so.0.1.0

#18 0x00007fac48569e65 in start_thread () from /lib64/libpthread.so.0

#19 0x00007fac4829288d in clone () from /lib64/libc.so.6

(gdb)