Handle pcp-dstat transition
Handle pcp-dstat transition

dstat is Python 2, never going to be updated and effectively
abandonded.  The replacement is pcp-dstat [1] which is mostly
compatible, with a few differences.  As distro start transitioning
(Fedora has), just drop the unsupported args for now.

[1] https://pcp.io/man/man1/pcp-dstat.1.html

Change-Id: Ibec8a37cb18a14656d97e2096c66bc8b21406068

dtroyer/devstack,openstack-dev/devstack,openstack-dev/devstack,nawawi/openstack,nawawi/openstack,dtroyer/devstack