Do not fail when getVSize is called on an inactive LV.

Change-Id: I0a8b6da4d57cdf810769586c1959989d7a545d0c
Bug-uri: https://bugzilla.redhat.com/show_bug.cgi?id=878955
Signed-off-by: Eduardo <ewarszaw@redhat.com>
Reviewed-on: http://gerrit.ovirt.org/9739
Reviewed-by: Yeela Kaplan <ykaplan@redhat.com>
Reviewed-by: Dan Kenigsberg <danken@redhat.com>