replace sleepUninterruptibly() with Thread.sleep() in tests

[EdColeman]

This is a subset (and supersedes) #3202 and focuses on replacements only in test code.

• replace occurrences of sleepUninterruptibly with Thread.sleep()
• prefer static import of TimeUnits instead of using TimeUnit.[UNIT] in files that had changes.

[ctubbsii]

Mostly okay with these changes, though I don't think most of them matter much, because we're not in the habit of interrupting threads in our test classes or killing the tests... if we do, it's likely we're just killing the entire test to start all over, so having the code try to deal with the interruption isn't really worth it. In a few cases, I think it would be cleaner to allow the InterruptedException to fall through the @Test methods rather than bother trying to handle them.

My favorite thing about these changes, though, is the static imports of the TimeUnit types, which is much more readable.