Use a default timeout of -1 when metadata_server_step and chunk_server_step don't set an explicit one

src/main_server.c

@@ -25,6 +25,8 @@ int metadata_server_main(int argc, char **argv)
     if (num_polled < 0) return -1;
     for (;;) {
         POLL(polled, num_polled, timeout);
+
+        timeout = -1;
         num_polled = metadata_server_step(
             &state, contexts, polled, num_polled, &timeout);
         if (num_polled < 0) return -1;
@@ -44,7 +46,10 @@ int chunk_server_main(int argc, char **argv)
         &state, argc, argv, contexts, polled, &timeout);
     if (num_polled < 0) return -1;
     for (;;) {
+
         POLL(polled, num_polled, timeout);
+
+        timeout = -1;
         num_polled = chunk_server_step(
             &state, contexts, polled, num_polled, &timeout);
         if (num_polled < 0) return -1;