Sync: Print name of manifest server used for smart sync/smart tag

When syncing using smart sync or smart tag mode, print the url of
the manifest server that is being used.

This is useful in organisations that have multiple manifest servers
used in different manifest branches.

Change-Id: Ib5bc2de5af6f4a942d0ef735c65cbc0721059a61

subcmds/sync.py

@@ -496,6 +496,8 @@ later is required to fix a server side protocol bug.
         sys.exit(1)
 
       manifest_server = self.manifest.manifest_server
+      if not opt.quiet:
+        print('Using manifest server %s' % manifest_server)
 
       if not '@' in manifest_server:
         username = None