[logging] drop locking inside log_msg (part 1)

looking at the code, there are only few calls to log_msg happening outside
of locking context (error reports when failing to grab the lock).
Everything else appears to be safe.

drop the attempt to lock inside log_msg for now, part 2 will address those
few calls that can happen outside of locking context.

Signed-off-by: Fabio M. Di Nitto <fdinitto@redhat.com>