Podman: review usage of privileged and cap_add flags

[mfarina1]

Review usage of privileged and cap_add flags for nm-manager containers. These flags sometimes behave differently in Podman, and it is best practice not to use them if not actually needed.

[DavidEdell]

The privileged and cap_add flags are currently used only by the ion-* containers. The usage of these flags is not causing any issues under podman for common use cases. It is possible that these flags are not behaving under podman the same as they do under Docker, indicating that their usage may not be required in the first place.