udev-rules: make tape devices also accessable by ENV{ID_SCSI_SERIAL}

udev-rules: make tape devices also accessable by ENV{ID_SCSI_SERIAL}

Tape and tape changer devices from Amazon Webservice Storage Gateway VTLs
and maybe other iSCSI VTLs all have the same ENV{ID_SERIAL}.
The results is, that only the last device is available in
/dev/tape/by-id/, as the former devices have been overwritten.
However, the devices can be distinguished by ENV{ID_SCSI_SERIAL}.

ENV{ID_SCSI_SERIAL} is not set on directly connected SCSI devices.

This rule additional creates links based on the ENV{ID_SCSI_SERIAL}, if
it is set.

In my case, it creates (ID_SCSI_SERIAL)
/dev/tape/by-id/scsi-AMZN_SGW-6BF81D02_MC_00001
/dev/tape/by-id/scsi-AMZN_SGW-6BF81D02_TD_00001
/dev/tape/by-id/scsi-AMZN_SGW-6BF81D02_TD_00002
...

instead of only (ID_SERIAL)
scsi-2414d5a4e5f5347572d364246