Remove a double write lock of the contexts lock in ast_wrlock_contexts().

How did this ever work?

(closes issue #12219)
Reported by: ys
Patches: 
      pbx.c.diff uploaded by ys (license 281)


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@108894 65c4cc65-6c06-0410-ace0-fbb531ad65f3

main/pbx.c

@@ -7823,7 +7823,7 @@ int ast_wrlock_contexts()
 	int res = ast_rwlock_wrlock(&conlock);
 	if (!res)
 		ast_atomic_fetchadd_int(&conlock_wrlock_version, 1);
-	return ast_rwlock_wrlock(&conlock);
+	return res;
 }
 
 int ast_rdlock_contexts()