Post Splunk 7.0 there is a simpler way to handle this. There is an endpoint that you can do a POST to, that cancels the bundle push operation, and gets the stuck cluster master out of the validate loop.
For more details, check these below links,
http://docs.splunk.com/Documentation/Splunk/7.0.0/RESTREF/RESTcluster#cluster.2Fmaster.2Fcontrol.2Fdefault.2Fcancel_bundle_push
http://docs.splunk.com/Documentation/Splunk/7.0.0/Indexer/Configurationbundleissues
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