Don't quote {posargs} in tox.ini
Don't quote {posargs} in tox.ini

Quotes around {posargs} cause the entire string to be combined into one
arg that gets passed to stestr. This prevents passing multiple args
(e.g. '--concurrency=16 some-regex')

Change-Id: I554926367bb01b3f77c664bad2c43cb6f529d9d8

openstack/senlin,openstack/senlin,stackforge/senlin,openstack/senlin,stackforge/senlin