vm: Remove redundant if statements in hotUnplugDisk

Change-Id: I2eb36e58526b0ce585cb1ea34dcca34921459a20
Signed-off-by: Yeela Kaplan <ykaplan@redhat.com>
Reviewed-on: http://gerrit.ovirt.org/17669
Reviewed-by: Mark Wu <wudxw@linux.vnet.ibm.com>
Reviewed-by: Dan Kenigsberg <danken@redhat.com>