isRunning didn't check local variable before reading saved data

All internal svdsm files contained last svdsm instance info,
after restart we didn't verify local manager instance before processing
the operation and got AttributeError exception when calling svdsm
manager.

This returns false when _svdsm instance is None or in firstLaunch.

Change-Id: I9dec0c6955dadcd959cc1c8df4e9745322fb0ce3
Bug-Id: https://bugzilla.redhat.com/show_bug.cgi?id=890365
Signed-off-by: Yaniv Bronhaim <ybronhei@redhat.com>
Reviewed-on: http://gerrit.ovirt.org/10491
Reviewed-by: Ayal Baron <abaron@redhat.com>
Reviewed-on: http://gerrit.ovirt.org/11135
Reviewed-by: Dan Kenigsberg <danken@redhat.com>
Reviewed-by: Douglas Schilling Landgraf <dougsland@redhat.com>
Reviewed-by: Federico Simoncelli <fsimonce@redhat.com>
Tested-by: Federico Simoncelli <fsimonce@redhat.com>