validate: seek_with_stop test randomly failing

The new test check.gst-editing-services.seek_with_stop is sometimes failing on master with

  * critical error Mismatch error in pad audiosink:sink, line 7. Expected:
event segment: format=TIME, start=0:00:00.000000000, offset=0:00:00.000000000, s
top=0:00:00.500000000, flags=0x01, time=0:00:00.000000000, base=0:00:00.00000000
0, position=0:00:00.000000000
Actual:
event segment: format=TIME, start=0:00:00.000000000, offset=0:00:00.000000000, s
top=0:00:00.500000000, flags=0x01, time=0:00:00.000000000, base=0:00:00.00000000
0, position=none

It seems just the position value that differs.