LCB assertion failure after CB Server restart

Situational test are failing against master after a recent change. The test scenario is restarting CB on all nodes (i.e running `service couchbase-server stop`), after stopping CB, the lcb_assertion here fails:

[410.29 INFO] (SDKD log:137) SDK version changeset ab445c264cd33c69fdc91c5b53d1ce2ec6f56cb4sdkd_lcb: /root/jenkins/workspace/server-build-test-lcb/centos-lcb-sdk-server-situational-tests/libcouchbase/src/getconfig.cc:36: void ext_callback_proxy(mc_PIPELINE*, mc_PACKET*, lcb_STATUS, const void*): Assertion `server->has_valid_host()' failed.

This was introduced in this patchset http://review.couchbase.org/c/libcouchbase/+/136712/7/src/getconfig.cc The issue has occurred against recent builds for 6.6.1, and 7.0.0.

I will attach logs (they were not automatically collected as the failure is treated as a crash).