Revert "Make heat the default collection method"

This reverts commit 6b478e9d90bce18b03f5411822897740f68c3dd0.

We will break anybody who is expecting CFN to be tried in all
circumstances with this. We probably just need to base which collectors
to try on what configuration we have, and not log warnings on
unconfigured collectors.

Change-Id: I4bf7d6f9af9487bf9d2c0942381c0ba68fc03ee9