utils: cleanup CURL handle when the POST value can't be fetched from …

…the PVAR

- patch provided by mikomarrache on GH #88

(cherry picked from commit b88e165)

modules/utils/functions.c

@@ -110,6 +110,7 @@ int http_query(struct sip_msg* _m, char* _url, char* _dst, char* _post)
 
     	if (fixup_get_svalue(_m, (gparam_p)_post, &post_value) != 0) {
 		LM_ERR("cannot get post value\n");
+		curl_easy_cleanup(curl);
 		pkg_free(url);
 		return -1;
     	}