Make quotas context cleanup lazy

*) Clean up service quotas only if they were changed.
*) Code clean up in setup() and cleanup() to avoid copy paste
*) Use append instead of extend in quotas tests
*) Init clients as well lazy
*) Add functional tests for quotas
*) Fix names of nova quotas
*) Fix don't break everything if you are not able to delete quota

Closes-bug: #1329907
Closes-bug: #1329795
Closes-bug: #1329379

Change-Id: I2ea781f08a731500bfff85e4c25e9786108b8b70