Include pipeline option for using identity headers

There have been patches in nova, glance client and glance
registry to give the user the option of not reauthenticating
in glance. Below are the related reviews. This patch
provides pipeline options the users will want to use for the same.

Nova: https://review.openstack.org/#/c/37070/
Glanceclient: https://review.openstack.org/#/c/37062/
Glance Registry: https://review.openstack.org/#/c/36563/

Change-Id: I904f8bafb7e5abceac5723ed8504c672a00c5ec7
Merge "Include pipeline option for using identity headers"