Merge same db calls for some quota methods

db.quota_get_all_by_project is called twice in method limit_check()
and reserve(),
db.quota_get_all_by_project_and_user is called twice in method
get_settable_quotas() in nova/quota.py

Change-Id: Ie5e3a414d3d52964c16613f44fe60a7f68bc0c66
Closes-bug: 1277068
Merge "Merge same db calls for some quota methods"