SCSI: Update the sense code for PREVENT REMOVAL errors

Change the sense codes for failures to eject a device that is locked
by PREVENT_ALLOW_MEDIUM_REMOVAL from
the generic MEDIA_LOAD_OR_EJECT_FAILED to the more specific
MEDIUM_REMOVAL_PREVENTED.

The second sense code is more accurate, and is also listed in MMC annex F
for the recommended sense codes for MMC devices while the first sense code is not.

Signed-off-by: Ronnie Sahlberg <ronniesahlberg@gmail.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
