Fix quota updating when admin deletes common user's volume

Add 'project_id=None' optional argument in QUOTAS related methods.

There are two problems when admin deletes volumes of common user
before fixing this bug:
Firstly, It will get tenant quotas using context.project_id which
results in getting admin's quotas not common user's.
Secondly, It will also get wrong quota usages using context.project_id
when updating common user's quota_usages.

So we could pass into QUOTAS related methods an optional argument to
specify the tenant ID to be affected. And if it's not set, then we
default to drawing the tenant ID from the context.

Fixes: bug 1078668
Change-Id: Ie250da84726d1c5c3280430038184000dfd1e9e2
Merge "Fix quota updating when admin deletes common user's volume"