Print security groups as a human readable list

Convert the security group list into a list that is more suitable for
printing.

Change-Id: I411d9256145986fad7659a9377494e29a6d70ced
Flatten hypervisor-show dictionary for printing

Flatten the nested dicts so that hypervisor information can be more
easily used at the command line.

Change-Id: I5dfcf9d10f917a63bde09f0b5a691784a5e8f02b
Closes-bug: #1243512
Merge "Print security groups as a human readable list"
Merge "Flatten hypervisor-show dictionary for printing"