It's not really possible to fit all sense codes into errno codes,
especially in such a way that sense codes can be properly categorized as
either guest-recoverable or host-handled. Create a new function that
checks for guest recoverable sense, then scsi_sense_buf_to_errno only
needs to be called for host handled sense codes.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>