It is more accurate to report that the test was skipped rather than
succeeded if we did not get to run it because it requires root.
Tested by running `make check` and inspecting the log file:
$ cat test/udev-test.pl.log
Must have root permissions to run properly.
SKIP test/udev-test.pl (exit status: 77)
The `make check` output also reported:
SKIP: test/udev-test.pl
We now verify the existence of uid's before applying them to devicenodes, so change the
test accordingly. We assume that both uid/gid 1 and 2 exist on the test system.