Backport relevant 2.0 repl tests

Some riak tests in 2.0 are relevant to the 1.4.12 release.  So far I have added repl_fs_stat_caching, since stat caching was backported by @jonmeredith to 1.4. Also, repl_location_failures is good since the AAE fullsync noisy logs PR touched that code. In fact, this PR shows there is a problem with the AAE fullsync noise reduction: the error and retry exit counts are broken when location_down messages are received when partition is not available.
It certainly does.  It seems to rely on the timeout for the test itself.  The code that runs the test in 2.0 has a timeout after which the test is stopped (configurable). That is not present in 1.4. I'm going to backport that too. Good find.