Don't use harness dir to find cookbooks

For projects that want to use ec-metal with the harness dir not being the ec-metal repo (like CSTA) the local cookbooks (ec-common, ec-harness, and private-chef) need to be locatable.

This change causes the recipes to look in ECM_LOCAL_COOKBOOKS instead of harness dir for those cookbooks.  I feel dirty using an env var so if people have a better suggestion I'm all ears.

I tested this manually by bringing up an ec2 server.  Running vagrant now.

Note: This makes provision[initial] from the jm/upgrade branch of csta run without error.