Fix WaitLogger#wait_for when :or_error flag present

[npj]

• WaitLogger#check_waiting returns tre or false explicitly based on whether or not the interests match, rather than the number of remaining interests, which may still include the :or_error flag
• adds a test that the expected result is obtained when multiple wait_for calls are in play. It should be noted that the patch eliminates a potential race condition where Thread.current['result'] was being overwritten by a later message that did not necessarily match any interests. Reproducing this race condition in the test is extremely challenging, if not impossible.

[jmettraux]

Many thanks!

[jmettraux]

Hello,

I ran your test against the unfixed version and it breaks from time to time, so the test is great (the CI is now watching that closely thanks to your test).

So, once again, many thanks!

John

[npj]

Excellent! Again, I'm happy to have made a contribution.

Peter