Retrieve security group quotas from Neutron if enabled

Secuirty group quota information in Project overview charts,
Admin defaults panel, and Admin create/update project is
retrieved from Neutron secuirty group is enabled.

Neutron security group is enbled when Neutron is used Neutron
security group extension is supported by a backend plugin.

Also removes the logic to remove quotas of floating IP and fixed IP
when neutron is enabled in dashboards/admin/defaults/tabs.py.
quotas.get_default_quota_data() already handles it properly
and this logic is no longer required.

Closes-Bug: #1212600

Change-Id: I59f069931fad519ca4ec135b92df0040ec8fc230