Do not create build requests for workers if offline longer than 30 minutes.

Author: gkistanova

Diff for: buildbot/osuosl/master/master.cfg

@@ -39,6 +39,8 @@ c['workers'] = config.workers.get_all()
 
 c['protocols'] = {'pb': {'port': "tcp:9990:interface=127.0.0.1" if test_mode else 9990}}
 
+c['ignoreOfflineWorkersTimeout'] = 30 # minutes.
+
 ####### CHANGESOURCES
 
 ##from buildbot.changes.pb import PBChangeSource