Redis ganglia metrics: support password param

This change makes the redis::ganglia class get the password that was supplied
to the parent 'redis' class and adds that to the metric pyconf file. Support
for a password parameter appears to already be present in the Python metric
module itself.

Change-Id: I3522d8619c37acfdb132728064051d5a28d4b1d7
Merge "Redis ganglia metrics: support password param" into production