RFR 8011799: CompletableFuture/Basic.java fails intermittently

[Chris Hegarty]

Silly mistake in the test. Incorrectly assumes that one of the given 
CompletableFutures must be completed before applyToEitherXXX / 
acceptEitherXXX / runAfterEitherXXX / anyOf returns. The correct 
assertion is that one of the given CompletableFutures must be completed 
before the return CompletableFuture completes.

With the given structure of the test this can be done by checking that 
one of the given CompletableFutures is complete after joining the 
returned CompletableFuture.

http://cr.openjdk.java.net/~chegar/8011799/webrev.00/webrev/test/java/util/concurrent/CompletableFuture/Basic.java.udiff.html

-Chris.