virISCSIScanTargets: Honour iSCSI interface
    
    When scanning for targets, iSCSI might give different results
    depending on the interface used. This is basically just name of
    config file under /etc/iscsi/ifaces to use. The file contains
    initiator IQN thus different results claim.
    
    Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
    Reviewed-by: John Ferlan <jferlan@redhat.com>