Fix for 2648

1. If validate perms (validating the parent obj etc) fails, the action done by http_post_collection is not undone. In the case of instance-ip/floating ip, we may endup leaking a route.
2. Subnet allocator zookeeper is not deleted on delete of subnet or on update of virtual network
3. Retry of delete node doesn’t pass recursive flag
4. Confusing stevedore error due to parameter mismatch

Fix:
1. Move all validation before starting to make state changes. (http_post, http_put)
    2. For all state modification, append a cleanup routine and walk the clean up routine in failure path
    3. Added “Failure/Cleanup” hook for all required classes.
    4.  Fix the parameter list for stevedore extension method
    5. Fix subnet delete to pass correct subnet name(which should include virtual network fq name)

Sanity report: http://10.204.216.50/Docs/logs/0000_2014_03_25_17_23_01/test_report.html