sync sslutils to not conflict with oslo.messaging

oslo.messaging changed and shipped nova/openstack/common/sslutils.py
in their own tree before it was changed in oslo-incubator. This
created conflicting options with nova, and caused the config
generator to explode (this also would have exploded if we used
any of the sslutils code in the gate, which we don't).

This is a sync of the finally merged oslo-incubator fix (which is
just periods in comments). This now makes the sslutils declaration
the same in both nova and olso.messaging.

Change-Id: I5cf392215825b604f0e3fe9546591a1e754d4478
Closes-Bug: #1287542