Removed unused iso8601 dependency

It should have been removed when migrating to oslo.utils when we dropped
timeutils module from our tree.

Change-Id: I4093a3c8faf3da5790ee31fdebec0b8ed70f84f3
Updated from global requirements

Change-Id: I181fc4f2b066eca08f2f23c5d2ff996aa46795ab
Merge "Removed unused iso8601 dependency"
Merge "Updated from global requirements"