Fix Popen arguments and other similar initialization
Fix Popen arguments and other similar initialization

Popen expects cwd to be None if not set, so don't set to an empty
string instead.

Signed-off-by: Jeff Peeler <d776211e63e47e40d00501ffdb86a800e0782fea@redhat.com>

steveb/heat-cfntools,openstack/heat-cfntools,sdake/heat-jeos,bbandaru/heat-cfntools,steveb/heat-cfntools