Add nova command 'get-policy'.

Returns the policy applied to a launched instance by vmspolicyd.
Relates to OS-182 and GC-92.

Change-Id: I476634afb48ee2634a6794250a13ce89ae0f60a6
Merge "Add nova command 'get-policy'." from grizzly/1.5

syncing grizzly/1.5 and havana/1.5, no additional changes made.

Change-Id: Ifb94d9818328f07c7ff75d95fb87b382129a7029