#1056 stop thread if connection with server is lost

Abort command if the connection with the server is lost.

Otherwise, a race condition that leaves ogServer and ogClient
out-of-sync might occur:

1. ogClient is busy running a command (on the worker thread), for example,
   image/restore.
2. ogServer is stopped OR ogClient loses connection with ogServer (due to
   transient network problem).
3. ogClient reconnects and ogServer sends a refresh command.
4. ogClient worker thread finishes and it sends a reply to image/restore.
5. ogServer gets confused because it expects a reply to the refresh
   command, not the old image/restore.

src/ogClient.py

@@ -100,6 +100,7 @@ class ogClient:
 
 		if len(data) == 0:
 			self.sock.close()
+			self.ogrest.kill_process()
 			self.connect()
 			return