Add basic capability to disrupt container network

[inbarshani]

Use pumba to disrupt a container's network.
Missing capabilities:

• Remove disruption (currently has to be done manually with 'docker exec')
• Disrupt once (currently using Pumba interval, although it isn't relevant)
• Use 'qdisc change' verb instead of 'qdisc add' (requires Pumba state management to be aware of previous 'add' and use 'change' instead)

[alexei-led]

Inbar, please rebase your pull request.