Previously it returned "yes" and empty graph with all labels having
value "0". Also remove bogus "multigraph redis" line.
TODO: die() in get_conn() makes this plugin to fail if any Redis
instance can't be connected.
This is a replacement for the redis_ plugin
Changes in the replacement:
* Supports multiple redis instances
* Supports AWS elasticache and other environments where the CONFIG
command is disabled
* Uses multigraph to separate graphs by instance