Unbreak python-swiftclient gate
Unbreak python-swiftclient gate

Need to correct how swift_store_endpoint is defaulted.

Currently:

swift_store_endpoint = None

will initialize it as a string, which would cause a 'ClientException:
Unsupported scheme' exception to be raised by head-of-tree swiftclient.

This was breaking the swiftclient gate (gate-tempest-dsvm-neutron-src-python-swiftclient).

Change-Id: I1044632683203f17543fd5a98ebf36b3004c5ad0
Closes-bug: 1424754

takeshineshiro/glance,scripnichenko/glance,akash1808/glance,stevelle/glance,dims/glance,jumpstarter-io/glance,klmitch/glance,saeki-masaki/glance,JioCloud/glance,paramite/glance,ozamiatin/glance,wkoathp/glance,JioCloud/glance,vuntz/glance,wkoathp/glance,vuntz/glance,darren-wang/gl,sigmavirus24/glance,dims/glance,ozamiatin/glance,kfwang/Glance-OVA-OVF,paramite/glance,openstack/glance,klmitch/glance,takeshineshiro/glance,openstack/glance,openstack/glance,darren-wang/gl,akash1808/glance,stevelle/glance,kfwang/Glance-OVA-OVF,sigmavirus24/glance,rajalokan/glance,scripnichenko/glance,rajalokan/glance,jumpstarter-io/glance,saeki-masaki/glance