res_pjsip: Fix memory leak of nameservers in off-nominal resolver creation failure.

Thanks Walter Doekes!
........

Merged revisions 410844 from http://svn.asterisk.org/svn/asterisk/branches/12


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@410845 65c4cc65-6c06-0410-ace0-fbb531ad65f3

res/res_pjsip/config_system.c

@@ -201,6 +201,7 @@ static int system_create_resolver_and_set_nameservers(void *data)
 		status = pjsip_endpt_create_resolver(ast_sip_get_pjsip_endpoint(), &resolver);
 		if (status != PJ_SUCCESS) {
 			ast_log(LOG_ERROR, "Could not create DNS resolver(%d), resorting to system resolution\n", status);
+			ao2_ref(discovered_nameservers, -1);
 			return 0;
 		}
 	}
@@ -241,4 +242,4 @@ static int system_create_resolver_and_set_nameservers(void *data)
 void ast_sip_initialize_dns(void)
 {
 	ast_sip_push_task_synchronous(NULL, system_create_resolver_and_set_nameservers, NULL);
-}
+}