scsi: fix device removal race vs IO restart callback on resume

scsi: fix device removal race vs IO restart callback on resume

There is (mostly theoretical) race between removal of a scsi device and
scsi_dma_restart_bh.

It used to be easier to hit this race prior to my / Paulo's patch series
that added rcu to scsi bus device handling code, but IMHO this race
should still be possible to hit, at least in theory.

Buglink: https://bugzilla.redhat.com/show_bug.cgi?id=1854811
Fix it anyway with a patch that was proposed by Paulo in the above bugzilla.

Suggested-by: Paolo Bonzini <[email protected]>
Signed-off-by: Maxim Levitsky <[email protected]>
Message-Id: <20201210125929.1136390[email protected]>
Signed-off-by: Paolo Bonzini <[email protected]>