make sure .get() also updates _info

Having the _info get out of sync with the actual attributes is kind of a
trap for the unwary. _info is used in preference to the attributes in
many places, and letting it get out of sync means that the method of
retrieval (get() vs. list()) influences the result.

Change-Id: I9d9bf086fa790b811c520b2fa317f95cb1921805
Support force update quota

Once we have additional check when update quota in
https://review.openstack.org/#/c/25887/, we need provide --force option
when run 'nova quota-update'.

Fix bug 1160749

DocImpact

Change-Id: Ib8d94d4eaa846f620abad5fb55017ac3fb0b322a
Merge "Support force update quota"
Merge "make sure .get() also updates _info"