vm: do not pause during refreshVolume

There's no need to pause the VM during the logical volume refresh as LVM
is taking care of freezing the IO during the dm table update.

Bug-Url: https://bugzilla.redhat.com/show_bug.cgi?id=889097
Change-Id: I896993c00b94c3255ad2007486e0589bf10b3a98
Signed-off-by: Federico Simoncelli <fsimonce@redhat.com>
Reviewed-on: http://gerrit.ovirt.org/8382
Reviewed-by: Ayal Baron <abaron@redhat.com>
Reviewed-by: Allon Mureinik <amureini@redhat.com>
Reviewed-on: http://gerrit.ovirt.org/24038
Reviewed-by: Dan Kenigsberg <danken@redhat.com>