Respect gc.enabled property while dropping tables

[aokolnychyi]

I think we should respect gc.enabled property while dropping tables. I am afraid we can create a table through snapshot and dropping it will actually delete files in the original table.

[aokolnychyi]

Thoughts, @RussellSpitzer @rdblue @pvary @rymurr @shardulm94?

[aokolnychyi]

The unfortunate part is that our docs advise to call DROP on snapshot tables, potentially messing the original table.

[aokolnychyi]

Let me submit a PR.