scsi: Force error for SCSI pools on virStorageBackendSCSIFindLUs failure
Related to :
https://bugzilla.redhat.com/show_bug.cgi?id=1171933
Rather than ignore the return status from virStorageBackendSCSIFindLUs,
cause a failure to start the pool if a -1 is returned. Issue was noted
during testing of the bz for iscsi that 'scsi' and 'fc' pools don't fail.