Deadlock when using not initialized security database

[AlexPeshkoff]

When 2 clients almost immediately try to attach to server in a cache of SecDB attaches takes place classic deadlock - 2 threads hold 2 mutexes and each tries to lock another one. Sooner of all same error may happen for all other errors when initializing lookup for users in security database but I noticed a bug and was able to reproduce it with not initialized security database.