Per discussion in BF-9418 we should blacklist the problematic tests. 

> spencer added a comment - Sep 05 2018 09:56:08 PM GMT+0000
Okay I spoke with Max offline. There are in fact some things these tests do that are a bit special. We aren't seeing this suite failing on random tests due to general slow machine issues. So blacklisting the problematic operations/tests seems like the best we can do for now, until we have a way for the test thread to communicate with the stepdown thread and indicate that it should slow down the stepdowns because it's been stuck retrying the same operation.

I think just blacklisting these tests from the stepdown suite entirely is probably sufficient. If the test blacklist winds up growing long over time due to other tests exhibiting similar behavior then I think we'll want to re-evaluate.

Sending back to TIG to implement the fix.