Remove oslo.uuidutils

The only use of uuidutils in barbican is generate_uuid
which will be dropped from oslo-incubator.

This patch moves generate_uuid to barbican.common.utils and
updates the context module from oslo.

Following changes were updated in context:

13eb01c Adding domain to context and log
12bcdb7 Remove vim header
bdabd51 Remove uuidutils imports in oslo modules
44e8222 Revert "Removes generate_uuid from uuidutils"
571a78a Removes generate_uuid from uuidutils
36859e5 Adding instance_uuid to context and log

Change-Id: If27f8308f00ce92d8cde0bc1c669c8020137eba5
Partial-bug: #1253497