Summary:
Was broken by https://github.com/facebook/rocksdb/issues/6660

Travis times before this change, after 6660:
platform_dependent: 17 min
group 1: 15 min
group 2: 44 min (often timeout on non-x86 or non-Linux)
group 3: 31 min
group 4: 21 min

After this change:
TODO

Pull Request resolved: https://github.com/facebook/rocksdb/pull/7360

Test Plan: CI inspection

Reviewed By: ajkr

Differential Revision: D23586917

Pulled By: pdillinger

fbshipit-source-id: 4c67cf33180b0b833c39a817e6c1f128727941d2