iotests: Drop TEST_DIR filter from _filter_nbd

Sockets should be placed into $SOCK_DIR instead of $TEST_DIR, so remove
the $TEST_DIR filter from _filter_nbd.

Signed-off-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-id: 20191017133155.5327-24-mreitz@redhat.com
Reviewed-by: Thomas Huth <thuth@redhat.com>
Signed-off-by: Max Reitz <mreitz@redhat.com>

tests/qemu-iotests/common.filter

@@ -221,7 +221,6 @@ _filter_nbd()
     # Filter out the TCP port number since this changes between runs.
     $SED -e '/nbd\/.*\.c:/d' \
         -e 's#127\.0\.0\.1:[0-9]*#127.0.0.1:PORT#g' \
-        -e "s#?socket=$TEST_DIR#?socket=TEST_DIR#g" \
         -e "s#?socket=$SOCK_DIR#?socket=SOCK_DIR#g" \
         -e 's#\(foo\|PORT/\?\|.sock\): Failed to .*$#\1#'
 }