Auto-set required FM environment variables.

[petewall]

To enable Fleet Management, we require several environment variables:

• GCLOUD_RW_API_KEY - Typically the same as the remote config password
• CLUSTER_NAME - The same as .cluster.name
• POD_NAME - From fieldPath: metadata.name
• NAMESPACE - From fieldPath: metadata.namespace
• GCLOUD_FM_COLLECTOR_ID - Built from the above

None of these require user-interaction, and they end up being very verbose...

We should use the "feature influence" to optionally automatically set these environment variables if they're not already set.