Fix tox cover command
Fix tox cover command

Add testr-args and coverage in tox cover command

Change-Id: I69192c464a36b42d97559534d2df19f737d58407
Closes-bug: #1571366

pshchelo/ironic,pshchelo/ironic,NaohiroTamura/ironic,openstack/ironic,NaohiroTamura/ironic,SauloAislan/ironic,openstack/ironic,SauloAislan/ironic,bacaldwell/ironic,bacaldwell/ironic,devananda/ironic