After https://github.com/redis/redis/pull/14226 module tests started
running with ASan enabled.
`auth.c` blocks the user on auth and spawns a thread that sleeps for
0.5s before unblocking the client and returning.
A tcl tests unloads the module which may happen just after the spawned
thread unblocks the client. In that case if the unloading finishes fast
enough the spawned thread may try to execute code from the module's
dynamic library that is already unloaded resulting in sefault.
Fix: just wait on the thread during module's OnUnload method.
d7b28ae74e