Fix update quota of subprojects

Fix update quota of subprojects

Cinder raises an exception when performing an update quota
operation in a subproject in which its parent's quotas weren't
explicitly updated.

This is because cinder will try to find the parent's quotas
in order to update the allocated value. But, since the parent's
quotas are the default quotas (i.e. there are no entries for them
in the database), the operation will raise an error.

Steps to reproduce:
1. Create a project A in keystone;
2. Create a project B in keystone with A as its parent;
3. Try to update the quota value of any resources of project B
   (e.g. openstack quota set <id of B> --volumes 2)

This patch fix this bug by adding entries to the database when
performing an update quota operation in a subproject and there
are still no quota associated with the parent project.

Change-Id: Ia732ca9d5a5f59d3973c2656a27b666077c3402a
Closes-bug: #1495990