fix mongo auth logic to work when auth is enabled
more careful about dealing with missing passwords
fix redis check memory leak (fixes #325)

Since tags is a reference to a list, and we're appending tags to the list,
we keep adding the same tags over and over again, and the aggregator thinks
they're separate contexts, so it keeps creating new aggregation buffers for
them. Fix is to dedupe tags in the redis check
dedupe tags submitted to MetricsAggregator
version 3.4.4
fix up mongo logging
fix for dogstatsd test
add a timeout to zk check (fixes #310)
Avoid calling extra functions to dedupe tags if there are none
Merge remote-tracking branch 'origin/3.4.x'

Conflicts:
	aggregator.py