iotests: Let common.nbd create socket in $SOCK_DIR

In addition, drop the nbd_unix_socket assignment in 241 because it does
not really do anything.

Signed-off-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-id: 20191017133155.5327-6-mreitz@redhat.com
Reviewed-by: Thomas Huth <thuth@redhat.com>
Signed-off-by: Max Reitz <mreitz@redhat.com>

tests/qemu-iotests/241

@@ -23,8 +23,6 @@ echo "QA output created by $seq"
 
 status=1 # failure is the default!
 
-nbd_unix_socket=$TEST_DIR/test_qemu_nbd_socket
-
 _cleanup()
 {
     _cleanup_test_img

tests/qemu-iotests/common.nbd

@@ -19,7 +19,7 @@
 # along with this program.  If not, see <http://www.gnu.org/licenses/>.
 #
 
-nbd_unix_socket="${TEST_DIR}/qemu-nbd.sock"
+nbd_unix_socket="${SOCK_DIR}/qemu-nbd.sock"
 nbd_tcp_addr="127.0.0.1"
 nbd_pid_file="${TEST_DIR}/qemu-nbd.pid"
 nbd_stderr_fifo="${TEST_DIR}/qemu-nbd.fifo"