qemu-iotests: Speed up make check-block

Using /tmp, which is usually mounted as tmpfs, the quick group can be
quicker.

On my laptop (Lenovo T430s with Fedora 20), this reduces the time from
50s to 30s.
Signed-off-by: NFam Zheng <famz@redhat.com>
Reviewed-by: NMax Reitz <mreitz@redhat.com>
Signed-off-by: NKevin Wolf <kwolf@redhat.com>

tests/qemu-iotests-quick.sh

@@ -3,6 +3,6 @@
 cd tests/qemu-iotests
 
 ret=0
-./check -T -qcow2 -g quick || ret=1
+TEST_DIR=${TEST_DIR:-/tmp/qemu-iotests-quick-$$} ./check -T -qcow2 -g quick || ret=1
 
 exit $ret

tests/qemu-iotests/check

@@ -238,6 +238,7 @@ QEMU_NBD      -- $QEMU_NBD
 IMGFMT        -- $FULL_IMGFMT_DETAILS
 IMGPROTO      -- $FULL_IMGPROTO_DETAILS
 PLATFORM      -- $FULL_HOST_DETAILS
+TEST_DIR      -- $TEST_DIR
 SOCKET_SCM_HELPER -- $SOCKET_SCM_HELPER
 
 EOF