xlate_normal() held the mac_learning lock while calling
output_normal(). When running with patch ports, this could cause
xlate_actions() to be called again, possibly attempting to take a
write lock on the same learning table causing a deadlock. This patch
solves the problem by holding the lock for a very brief period of
time.
Bug #19423. Signed-off-by: Ethan Jackson <ethan@nicira.com> Acked-by: Justin Pettit <jpettit@nicira.com>