iotests: Make _filter_nbd support more URL types

This function should support URLs of the "nbd://" format (without
swallowing the export name), and for "nbd:///" URLs it should replace
"?socket=$TEST_DIR" by "?socket=TEST_DIR" because putting the Unix
socket files into the test directory makes sense.
Signed-off-by: NMax Reitz <mreitz@redhat.com>
Reviewed-by: NJohn Snow <jsnow@redhat.com>
Reviewed-by: NFam Zheng <famz@redhat.com>
Reviewed-by: NKevin Wolf <kwolf@redhat.com>
Signed-off-by: NKevin Wolf <kwolf@redhat.com>

tests/qemu-iotests/common.filter

@@ -238,7 +238,8 @@ _filter_nbd()
     #
     # Filter out the TCP port number since this changes between runs.
     sed -e '/nbd\/.*\.c:/d' \
-        -e 's#nbd:127\.0\.0\.1:[^:]*:#nbd:127\.0\.0\.1:PORT:#g' \
+        -e 's#nbd:\(//\)\?127\.0\.0\.1:[0-9]*#nbd:\1127.0.0.1:PORT#g' \
+        -e "s#?socket=$TEST_DIR#?socket=TEST_DIR#g" \
         -e 's#\(exportname=foo\|PORT\): Failed to .*$#\1#'
 }