Check ulimit when creating rocksdb storage

[carneiro-cw]

The limit of open files descriptors should be pretty high otherwise rocksdb can misbehave (sometimes even wipe the db) when starting. We should check if the ulimit is higher than some threshold before initialization.

[samueldurantes]

@carneiro-cw Is this issue available? Can you assign me?

[carneiro-cw]

The issue is available, we don't assign issues to people from outside the organization though. But feel free to open a PR.