Summary:
Run the basic range deletion tests against the standard set of
configurations. This testing exposed that files with hash indexes and
partitioned indexes were not handling the case where the file contained
only range deletions--i.e., where the index was empty.

Additionally file a TODO about the fact that range deletions are broken
when allow_mmap_reads = true is set.

/cc ajkr nvanbenschoten

Best viewed with ?w=1: https://github.com/facebook/rocksdb/pull/4021/files?w=1
Pull Request resolved: https://github.com/facebook/rocksdb/pull/4021

Differential Revision: D8811860

Pulled By: ajkr

fbshipit-source-id: 3cc07e6d6210a2a00b932866481b3d5c59775343