meson.build: move the leftover udev rule check up

meson.build: move the leftover udev rule check up

ninja executes the test in the same order but we don't want to waste 5 minutes
testing other things when we have a udev rule leftover from a previous run.

Plus, this test can't be run in parallel with others, so in the worst case we
had to wait for several long-running tests to finish before this one could be
started.

To avoid all this, let's move this up to be the first check.

Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>