Make the "daemons and web have different config" warning more specific

Summary:
I'm hitting this in the cluster and couldn't figure it out after staring at it for a couple minutes. Produce a better error.

This dumps a hash of each configuration key value which is set to a non-default value into the daemon log. This is much more compact than the full config, and doesn't spread secrets around, so it seems like a good balance between providing information and going crazy with it.

Test Plan: {F284139}

Reviewers: btrahan

Reviewed By: btrahan

Subscribers: epriestley

Differential Revision: https://secure.phabricator.com/D11699