[Mac Randomization] Fix perference changing not work and wrong default

value

1. Mac randomization setting would not effect, until reconnecting the network.
Disconnect it and WiFi will soonly connect back.
2. Mac randomization setting of adding network page is default to
"device MAC", correcting to "Randomization"

Bug: 123123123
Test: make RunSettingsRoboTests -j32 ROBOTEST_FILTER=com.android.settings.wifi
Change-Id: I91f8670ddf81aea89354c4cc9c9a7901b8f3409c