Description
What's the issue?
The 'TestClient' currently uses a 'sync.Mutex' to guard access to the underlying bucket/object map; we should be using a 'sync.RWMutex'. This means we're seeing deadlocks in 'cbbackupmgr' unit testing.
This won't guard against all potential deadlock conditions (e.g. iterating whilst creating new objects) but should cover our existing use case more sufficiently.