Use stock argparse behaviour for optional args
Use stock argparse behaviour for optional args

optparse would print "Options" but argparse prints "optional arguments".

The default argparse behaviour is fine, let's stick with that.

Change-Id: Ib53a2581af9d776e9a7c1cd90eebe89b70034e57

JioCloud/pbr,citrix-openstack-build/pbr,JioCloud/pbr,citrix-openstack-build/pbr,openstack-dev/pbr,klmitch/pbr,openstack-dev/pbr,WiFast/pbr,WiFast/pbr,citrix-openstack-build/pbr,varunarya10/pbr,redhat-openstack/pbr,klmitch/pbr,emonty/oslo-packaging,openstack-dev/pbr,varunarya10/pbr,emonty/oslo-packaging,redhat-openstack/pbr