Live security group additions and removals

[llukeell]

Problem:
Currently CloudStack requires an instance to be stopped before adding or removing a security group, causing unnecessary downtime. The underlying iptables rules are enforced at the hypervisor level and should not require instance downtime to modify.

Expected behavior:
Security groups can be added or removed from a running instance without a stop/start cycle.

CloudStack version: 4.21.0.0
Zone type: Security Group zone