Add enable_security_group option

Using noop driver to disable security group is confusing.
In this commit, we introduce enable_security_group in server side.

DocImpact
UpgradeImpact

Implements bp: security-group-config-cleanup
Related-Bug: 1112912
Change-Id: Ice44a4e2a519c64e613eeb24372de46726473339
Merge "Add enable_security_group option"