Speed Up Iteration of accounts by lock state

[Comeani]

At the bank code meeting today, we talked about how compiling the list of accounts that are unlocked on some cluster can be sped up:

The find_unlocked_account_names function returns a dictionary object with clusters as the keys and the list of unlocked accounts as the values. The key/value pair is not being utilized elsewhere however (need to double check this), so converting this to a set will help streamline how it is used in update_status.

At the level of the account lock state iteration, we could stop and continue on to the next account name if it is found to be locked on any cluster (currently iterating over all accounts on each cluster regardless).