Default Influx retention policy has infinite retention

[David00]

This is an issue reported by @mholzma and I've confirmed it in a fresh installation of the existing v0.3.1 release image. This will be fixed in the upcoming v0.4.0 release. However, it can also be fixed manually in the Influx terminal with:

(Note that running this will trim all data associated with the autogen retention policy older than 30 days!)

ALTER RETENTION POLICY "autogen" ON "power_monitor" DURATION 30d

> show retention policies;
name    duration shardGroupDuration replicaN default
----    -------- ------------------ -------- -------
autogen 0s       168h0m0s           1        true
rp_5min 0s       168h0m0s           1        false

The autogen RP should have a 30 day limit on it, like this:

> show retention policies;
name    duration shardGroupDuration replicaN default
----    -------- ------------------ -------- -------
autogen 720h0m0s 168h0m0s           1        true
rp_5min 0s       168h0m0s           1        false