container-spec: only use required CAP_*

[parthpower]

securityContext.privileged = true gives unnecessary permissions to containers.

Only use required capabilities with securityContext.Capabilities option

use different security contexts for them otg-gnmi-server and keng-controller since they don't need as many capabilities as TE and PE

[anjan-keysight]

Without explicitly assigning some security cap to controller & gnmi, the node mapped port is not accepting requests. It will need some capability to be assigned. I will investigate further, update this PR and then merge.

[parthpower]

Without explicitly assigning some security cap to controller & gnmi, the node mapped port is not accepting requests. It will need some capability to be assigned. I will investigate further, update this PR and then merge.

would need CAP_NET_BIND_SERVICE to bind to port number < 1024

[anjan-keysight]

The node ports are > 30000. I think we may have to add some explicit, minimal capability. I will investigate later this week.