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's designed to continually retry until the test harness times out, because of races in cluster membership.