https://bugzilla.redhat.com/show_bug.cgi?id=1174569

There's nothing we need to do for shared iSCSI devices in
qemuAddSharedHostdev and qemuRemoveSharedHostdev. The iSCSI layer
takes care about that for us.
Signed-off-by: NLuyao Huang <lhuang@redhat.com>
Signed-off-by: NMichal Privoznik <mprivozn@redhat.com>