Adds API Sample tests for FloatingIPDNS extension.

Partially implements blueprint nova-api-samples
Fixes bug 1070164

Change-Id: I4c3e5d406ce43c27bb49a651facaa831de646a66
Allow generic rules in context_is_admin rule in policy.

context_is_admin role is used by nova to check if
the current user is the admin. But it can only check
role rules. The fix allow generic rules in context_is_admin.

DocImpact

Fixes bug 1118142

Change-Id: Ib4823a67fe63d5356fc8c9280a2013b8855f5217
Merge "Allow generic rules in context_is_admin rule in policy."
Merge "Adds API Sample tests for FloatingIPDNS extension."