Sync common.context changes from olso

Sync changes to common.context, to remove the dependency on the uuidutils
module that's going to be removed from oslo.

Change-Id: Ibae8af811d7f5b7d6a1499f35288073e5d383e64
Remove openstack.common.uuidutils

Remove the oslo uuidutils module requirement.

Change-Id: Ic17282c87d6a95b64f3874e189f89c9f9f8be196
Merge "Sync common.context changes from olso"
Merge "Remove openstack.common.uuidutils"