uniq tests: Make uniq_test:stdout more reliable

[markj]

Summary

When running regression tests in paralle, this one occasionally fails
because uniq exits with status 0. I believe this is because the test is
a bit racy: it assumes that true(1) will exit before uniq writes to
standard out.

It is easy to reproduce this failure by running the test in a loop and
running a buildkernel in the background. Make the race smaller by
sleeping for a bit. Maybe there's a cleverer way to handle this?

[des]

usr.bin/uniq/tests/uniq_test.sh

171

I would increase this to 1 in case the test is ever ported to a platform where sleep(1) doesn't take fractional values. It's not like anyone will notice the delay.

174

replacing true with : (which is a shell builtin, while true may or may not be) might also help.

[markj]

usr.bin/uniq/tests/uniq_test.sh

174

Unfortunately, that doesn't do the trick.

[markj]

Apply feedback, don't use fractional times.