Populate table index -> column family mappings at start-up

[jonahcohen]

Currently the RocksDB-SE data dict is populated at startup with table -> index mappings, but those indices don't have mappings to their associated column families. The get_cf call returns null.

This relies on MySQL to open the table at some point in order to fill in the column families. For fast drop table, we need access to these column families even if the table hasn't been opened already.

[jonahcohen]

I think I can take this myself.

[jonahcohen]

https://reviews.facebook.net/D32955