Initialize timeout parameter to -1 in main_server.c

Fixed uninitialized timeout variables in metadata_server_main() and
chunk_server_main() functions by setting default value to -1.

**Changes:**
- metadata_server_main(): Changed `int timeout;` to `int timeout = -1;`
- chunk_server_main(): Changed `int timeout;` to `int timeout = -1;`

This ensures the timeout parameter has a defined default value before
being passed to init functions, which is important for predictable
behavior even though the init functions set the value themselves.

All build targets (tinydfs_server.out, example_client.out,
tinydfs_test.out) compile and run successfully.

src/main_server.c

@@ -18,7 +18,7 @@ int metadata_server_main(int argc, char **argv)
     void *contexts[MAX_CONNS+1];
     struct pollfd polled[MAX_CONNS+1];
     int num_polled;
-    int timeout;
+    int timeout = -1;
     MetadataServer state;
     num_polled = metadata_server_init(
         &state, argc, argv, contexts, polled, &timeout);
@@ -38,7 +38,7 @@ int chunk_server_main(int argc, char **argv)
     void *contexts[MAX_CONNS+1];
     struct pollfd polled[MAX_CONNS+1];
     int num_polled;
-    int timeout;
+    int timeout = -1;
     ChunkServer state;
     num_polled = chunk_server_init(
         &state, argc, argv, contexts, polled, &timeout);