SettingsProvider: Revert default WiFi sleep policy to "never"

Change Ie459b8e70fdbc7c605452fe0692d7bc26460e939 has the side effect of
altering the default WiFi sleep policy back to "default" (off when screen
turns off), which is contrary to the policy of "never" established in
I0598af41fe0144f2dfddc5bd331bd91d91e0ffea.

Change-Id: Id8b6a1abbf27ca653277399a0d8c84a121ff93c8