iotests: Make qemu_nbd_popen() a contextmanager
Instead of duplicating the code to wait until the server is ready and
remember to terminate the server and wait for it, make it possible to
use like this:
with qemu_nbd_popen('-k', sock, image):
# Access image via qemu-nbd socket...
Only test 264 used this helper, but I had to modify the output since it
did not consistently when starting and stopping qemu-nbd.
Signed-off-by: Nir Soffer <nsoffer@redhat.com>
Message-Id: <
20200727215846.395443-3-nsoffer@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Signed-off-by: Eric Blake <eblake@redhat.com>