Continue supporting persisting country code

Some devices rely on Setup Wizard to set a persistent country
code.
This CL honors the persistent option, fixing corresponding 5GHz AP
problem.
This also includes addtional unit tests for this change.

BUG=28127280
TEST=compile
TEST=runtest frameworks-wifi
Change-Id: I2f36216e143d0ac4959f26a9965def061a06aabf
4 files changed
tree: b30d35ba8001455ba1b1946824be8989d0ea72f3
  1. service/
  2. tests/