[2.1 backport] rocksdb: Include fix on improving SST IDs used in cache keys

[itsbilal]

Bumps up commit of RocksDB fork to pick up
cockroachdb/rocksdb#63 . This should resolve
some issues observed around out-of-order insertion of keys in SSTables.

Release note (bug fix): Fix a rare data corruption bug in RocksDB
caused by newer Linux kernel's handling of i_generation on certain
filesystems

[cockroach-teamcity]

This change is 

[petermattis]

LGTM

[garvitjuniwal]

thanks for the fix @itsbilal and @petermattis

does this bug also affect release-2.0? i'm wondering if a backport to 2.0 is also necessary or not.

[petermattis]

@garvitjuniwal Yes, I believe this bug affects all versions of RocksDB, so 2.0 as well. @itsbilal Can you backport to 2.0? @garvitjuniwal We're not currently making new 2.0 releases, but I believe that is ok in your case, correct?

[garvitjuniwal]

Yes @petermattis. We can merge your 2.0 backport into our internal branch and use it. We don't need a new release. Thank you!

[itsbilal]

@garvitjuniwal 2.0 backport is in progress: cockroachdb/rocksdb#65

Once this is in, I'll push a commit to update the rocksdb ref in release-2.0 in the cockroach repo to point to the patched version. You should then be able to merge that in.

[garvitjuniwal]

Thanks @itsbilal