Use "python -m coverage" instead of coverage cli
Use "python -m coverage" instead of coverage cli

As requested by the Debian package maintainer, this makes the
coverage report work more easily on Debian/Ubuntu

Change-Id: Ibed9e164c89543b679393ee18ccdb4a15bdea6d7
Closes-Bug: #1241330

NeCTAR-RC/heat,gonzolino/heat,rdo-management/heat,dims/heat,jasondunsmore/heat,pshchelo/heat,NeCTAR-RC/heat,dragorosson/heat,cwolferh/heat-scratch,openstack/heat,steveb/heat,rh-s/heat,rh-s/heat,openstack/heat,dims/heat,srznew/heat,cryptickp/heat,takeshineshiro/heat,redhat-openstack/heat,pshchelo/heat,noironetworks/heat,takeshineshiro/heat,dragorosson/heat,redhat-openstack/heat,steveb/heat,cwolferh/heat-scratch,maestro-hybrid-cloud/heat,gonzolino/heat,ntt-sic/heat,pratikmallya/heat,cryptickp/heat,maestro-hybrid-cloud/heat,pratikmallya/heat,ntt-sic/heat,miguelgrinberg/heat,srznew/heat,jasondunsmore/heat,miguelgrinberg/heat,noironetworks/heat,rdo-management/heat