Fix nonce1 and sessionid memory leak

util.c

@@ -1700,6 +1700,7 @@ static bool parse_extranonce(struct pool *pool, json_t *val)
   }
 
   cg_wlock(&pool->data_lock);
+  free(pool->nonce1);
   pool->nonce1 = nonce1;
   pool->n1_len = strlen(nonce1) / 2;
   free(pool->nonce1bin);
@@ -2527,6 +2528,8 @@ resend:
   }
 
   cg_wlock(&pool->data_lock);
+  free(pool->nonce1);
+  free(pool->sessionid);
   pool->sessionid = sessionid;
   pool->nonce1 = nonce1;
   pool->n1_len = strlen(nonce1) / 2;