Update how tokens are redacted

Using SHA-1 to match how Nova and Swift redact their tokens.
Was discussed in the below thread:

http://lists.openstack.org/pipermail/openstack-dev/2014-September/045802.html

Here's what nova went with: https://review.openstack.org/#/c/99511/
swift seem to be following suit: https://review.openstack.org/#/c/99632/

Change-Id: I3045d6d9d2a13770f4022dbbd474b34eb1032f6e
Closes-bug: 1329301
Merge "Update how tokens are redacted"