taskprocessor.c: Add CLI "core ping taskprocessor" missing unlock.

Change-Id: I78247e0faf978bf850b5ba4e9f4933ab3c59d17b

main/taskprocessor.c

@@ -399,6 +399,7 @@ static char *cli_tps_ping(struct ast_cli_entry *e, int cmd, struct ast_cli_args
 	ts.tv_nsec = when.tv_usec * 1000;
 	ast_mutex_lock(&cli_ping_cond_lock);
 	if (ast_taskprocessor_push(tps, tps_ping_handler, 0) < 0) {
+		ast_mutex_unlock(&cli_ping_cond_lock);
 		ast_cli(a->fd, "\nping failed: could not push task to %s\n\n", name);
 		ao2_ref(tps, -1);
 		return CLI_FAILURE;