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 3496971e61dc9f6e725e57fb7b5f0c57631bbfc2.
Reported By: Александр Недоцуков, brd

(cherry picked from commit 738314e445ceac4d3dd6c77c636044141623b8dc)