The problem is that a mysql connection instance is not thread-safe
and reentrant, meaning that it can't be used concurrently and can't
be re-entered while it's already running. This applies for any form
of the server (embedded or not), but this rule can be violated in a
test case if the test sends a new command without waiting for the
result of previous command that was sent asynchronously and this can
lead to hangs when over a network or to crashes under embedded server
as the server query execution path will be re-entered concurrently
with the same connection structure.

The solution is to rework the test case so that the aforementioned
rule is obeyed.