scsi-disk: do not complete canceled UNMAP requests Canceled requests should never be completed, and doing that could cause accesses to a NULL hba_private field. Cc: qemu-stable@nongnu.org Reported-by: Stefan Priebe <s.priebe@profihost.ag> Tested-by: Stefan Priebe <s.priebe@profihost.ag> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>