Instability with incremental backup tests (pg_combinebackup, 003_timeline.pl)

Hi all,

dikkop has reported a failure with the regression tests of pg_combinebackup:
https://buildfarm.postgresql.org/cgi-bin/show_log.pl?nm=dikkop&dt=2024-08-04%2010%3A04%3A51

That's in the test 003_timeline.pl, from dc212340058b:
#   Failed test 'incremental backup from node1'
#   at t/003_timeline.pl line 43.

The node is extremely slow, so perhaps bumping up the timeout would be
fine enough in this case (did not spend time analyzing it).  I don't
think that this has been discussed, but perhaps I just missed a
reference to it and the incremental backup thread is quite large.

Thanks,
--
Michael