fix: storage url

x-storage-url is now set in deuce.context through
openstack hook
hook: swift hook takes care of swift storage url

Also a new healthhook class was created, which is checked in all hooks
to return if its either a ping or health check.
refactor: hooks

rename Healthhook to HealthHook
rename SwiftHook to OpenstackSwiftHook
Merge pull request #99 from TheSriram/swift_storage_url_fix

fix: storage url