[wifi_score_params] Handle delete properly

Bug: 65216267
Test: adb shell settings put global wifi_score_params horizon=1
Test: adb shell settings delete global wifi_score_params
Test: adb logcat -d | grep ScoringParams:
Test: Make sure that after the delete, horizon param reverts to default
Change-Id: I455e383f9e0345a55b97ae941717b8c6841be98f
1 file changed