Add import for TestProbe

The example for TestProbe doesn't seem to work very well without the TestProbe class imported. :-(
=doc #15491 java circuit breaker doc update
=doc fix typo found in #15504 in the java version of docs
Merge pull request #15505 from ktoso/fix-typo-ktoso

=doc fix typo found in #15504 in the java version of docs
Merge pull request #15478 from kanerogers/patch-1

Add import for TestProbe
Merge pull request #15492 from gfaerie/master

=doc #15491 java circuit breaker doc update