Flush output to notify without blocking in http-disk-server callers

Signed-off-by: Ronan Abhamon <ronan.abhamon@vates.tech>

http_disk_server.py

@@ -386,6 +386,10 @@ def emit_server_ready():
         if STARTING_SERVER:
             eprint('Server ready!')
             STARTING_SERVER = False
+            # Flush to ensure we can read notification message
+            # in another process without waiting.
+            sys.stdout.flush()
+            sys.stderr.flush()
 
     httpd = None
     httpd_thread = None