Revert "lib/libc/net/nsdispatch.c: Fix missing unlock and add locking annotations"

This commit should not have introduced any functional changes, but
apparently it did. This appears to have broken LDAP setups.
Reverting for now. Will reland once I have fixed the breakage.

This reverts commit 5245bf7b92b74e556527b4916a8deba386fe5772.
Reported By: Александр Недоцуков, brd
MFC after: immediately