scsi-disk: Always report RESERVATION_CONFLICT to guest

scsi-disk: Always report RESERVATION_CONFLICT to guest

In the case of scsi-block, RESERVATION_CONFLICT is not a backend error,
but indicates that the guest tried to make a request that it isn't
allowed to execute. Pass the error to the guest so that it can decide
what to do with it.

Without this, if we stop the VM in response to a RESERVATION_CONFLICT
(as is the default policy in management software such as oVirt or
KubeVirt), it can happen that the VM cannot be resumed any more because
every attempt to resume it immediately runs into the same error and
stops the VM again.

One case that expects RESERVATION_CONFLICT errors to be visible in the
guest is running the validation tests in Windows 2019's Failover Cluster
Manager, which intentionally tries to execute invalid requests to see if
they are properly rejected.

Buglink: https://issues.redhat.com/browse/RHEL-50000
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Acked-by: Paolo Bonzini <pbonzini@redhat.com>
Message-ID: <20240731123207.27636-5-kwolf@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
(cherry picked from commit 9da6bd39f92434f55573acd017841b195c60188f)
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>