LCB crash following CB server restart for CB versions <6.5

There are issues with running against 6.0.3 and 5.5.6, that are not occurring with 6.5 (or 7.0 builds).

The particular error is happening with a Hybrid test (continually running KV sets/gets and View queries) on a Service restart test where we stop the CB server on each node, and then start them all again after 5 secs. The top level errors being reported on Jenkins are:

03:19:49 [362.67 INFO] (SDKD log:137) SDK version changeset 79e57914fc713e0eb96c583076576a3e44d2fe1a*** Error in `/root/jenkins/workspace/sdk-lcb-situational/sdk-lcb-situational-release/c-sdk-alice-up/sdkd-cpp/sdkd_lcb': corrupted double-linked list: 0x00007f6b54077c60 ***

Running this locally on my Mac I see a different, but probably related error:

sdkd_lcb(96018,0x70000edcf000) malloc: *** error for object 0x7f9c1962001d: pointer being freed was not allocated

And running with debug I get a stack of:

__pthread_kill 0x00007fff771cd2c2

pthread_kill 0x00007fff77288bf1

abort 0x00007fff771376a6

malloc_vreport 0x00007fff77246077

malloc_report 0x00007fff77245e38

mcreq_wipe_packet mcreq.c:276

mcreq_packet_done mcreq.c:888

mcreqpktflush_callback(void*, unsigned int, void*) mcreq-flush-inl.h:66

netbuf_end_flush2 netbuf.c:655

mcreq_flush_done_ex(mc_pipeline_st*, unsigned int, unsigned int, unsigned long long) mcreq-flush-inl.h:93

mcreq_flush_done(mc_pipeline_st*, unsigned int, unsigned int) mcreq-flush-inl.h:103

lcb::Server::finalize_errored_ctx() mcserver.cc:1153

lcb::Server::start_errored_ctx(lcb::Server::State) mcserver.cc:1122

lcb::Server::socket_failed(lcb_STATUS) mcserver.cc:1062

on_error(lcbio_CTX*, lcb_STATUS) mcserver.cc:1048

err_handler ctx.c:44

timer_callback timer.c:43

event_process_active_single_queue 0x000000010a660c4a

event_base_loop 0x000000010a65de76

::lcb_wait(lcb_INSTANCE *, lcb_WAITFLAGS) wait.cc:109

CBSdkd::Handle::postsubmit(CBSdkd::ResultSet&, unsigned int) Handle.cpp:427

CBSdkd::Handle::dsMutate(CBSdkd::Command, CBSdkd::Dataset const&, CBSdkd::ResultSet&, CBSdkd::ResultOptions const&) Handle.cpp:584

CBSdkd::WorkerDispatch::processRequest(CBSdkd::Request const&) Worker.cpp:177

CBSdkd::WorkerDispatch::selectLoop() Worker.cpp:308

CBSdkd::WorkerDispatch::run() Worker.cpp:330

CBSdkd::new_worker_thread(void*) Control.cpp:70

_pthread_body 0x00007fff772862eb

_pthread_start 0x00007fff77289249

thread_start 0x00007fff7728540d

Afaict this is an LCB issue. Let me know if you know whats going on, or you need anymore details from me.