glance/cinder/quantum counter units are not accurate/consistent

change floating ip counters to 'ip' unit
change volume.size counters to 'GB' unit
change image.[update/upload/delete] counters to 'image' unit

Change-Id: Icdb92b3edf08d9cf9ea555b3bdfe7d452dd3ffff
Fixes:bug1173287
Merge "glance/cinder/quantum counter units are not accurate/consistent"