Replace btsync with rsync
Fix errors in glance log

Disable other glance stores.
Use public keystone endpoint rather than admin endpoint.
Glance image rsync tweaks:

Do not overwrite files with newer timestamps, copy extended attributes
too.
Image sync: remove images deleted in DB

Use Glance DB as source of truth to determine which images to delete.
Glance image sync: rm -f to squelch already deleted errors
Merge pull request #464 from blueboxgroup/replace-btsync

Replace btsync with rsync