Update python-dracclient version
Update python-dracclient version

Update python-dracclient version to indicate Wallaby compatibility with
6.*.* releases.

Version 6.0.0 is available from PyPI [1].

[1] https://pypi.org/project/python-dracclient/6.0.0/

Change-Id: Ia7093a3ed48e19197f74da9e1c49416a974a76be

openstack/ironic,openstack/ironic