adding properties  isLibSCSI and isLinuxSGIO
adding properties  isLibSCSI and isLinuxSGIO

a  little extra effort so we dont have to use hasattr
to check the values . Also added more specific error
handling at the imports so you get at least a message
if we have a libiscsi or linux_sgio package around

rosjat/python-scsi,AHelper/python-scsi,AHelper/python-scsi