[JBIDE-15059] corrected creation of push operation

Removed the prior workaround that was fetching after the push. Replaced
it by a proper way of creating the push operation which makes sure that
the remote tracking branches get updated once the push is executed.

Conflicts:
	plugins/org.jboss.tools.openshift.express.ui/src/org/jboss/tools/openshift/express/internal/core/behaviour/OpenShiftServerPublishMethod.java