Handle requests for a non-existent account gracefully

[DougReeder]

1. Start Armadietto
2. Delete any accounts named 'test' or 'test2'
3. Run the API test suite against the server

Expected result: Armadietto logs a message indicated a client tried to access a non-existent account, at the 'warning' level

Actual result: Armadietto logs the message "Bad store.permissions implementation?" at the error level.