scsi-disk: fix bug in scsi_block_new_request() introduced by commit 137745c

scsi-disk: fix bug in scsi_block_new_request() introduced by commit 137745c

This patch fixes a bug in scsi_block_new_request() that was introduced
by commit 137745c5c60f083ec982fe9e861e8c16ebca1ba8. If the host cache
is used - i.e. if BDRV_O_NOCACHE is _not_ set - the 'break' statement
needs to be executed to 'fall back' to SG_IO.

Cc: qemu-stable@nongnu.org
Signed-off-by: Ulrich Obergfell <uobergfe@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
(cherry picked from commit 2fe5a9f73b3446690db2cae8a58473b0b4beaa32)
Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>