Truncate backup-retention-cronjob name for template in influxdb chart

[oxr463]

In _helpers.tpl, we have two places where we truncate names down to 63 characters. But then in the backup-retention-cronjob template, we append -backup-retention to the name; that's an extra 17 characters.

I suggest truncating the backup-retention-cronjob to 63 chars, we'll need to truncate it before we append the additional chars. Otherwise, the name won't make very much sense.

Or... We could provide a way to override the name in the values.yaml file?

Reference(s):

• https://github.com/influxdata/helm-charts/blob/master/charts/influxdb/templates/_helpers.tpl#L6
• https://github.com/influxdata/helm-charts/blob/master/charts/influxdb/templates/backup-retention-cronjob.yaml#L9