Docloader failures prints rest password in cleartext and failures are not marked in UI

Trying to load sample bucket while rebalancing was going on. As expected, docloader would fail as, we cant create buckets while rebalancing.

The error shown on the screen is very uninformative.

Moreover, the logs contain the rest password in cleartext.
"Cannot create buckets during rebalance\"}\n

{'username': 'Administrator', 'node': '10.3.2.46:8091', 'password': 'password', 'bucket': 'beer-sample', 'ram_quota': 100}

"