Settings: fix prompt celluar->wlan dialog in wifi settings

When user chooses "Manually" for "celluar->wlan" in advanced
wifi settings, still can see dialog is prompted even current
screen is wifi settings.

No need to prompt dialog when currently in wifi settings
because currently user can see the SSID list. Create one
activity only for wifi use to easily identify wifi settings.

Change-Id: I00d4637132b8f62bec5941505494710d88d4ee5c
CRs-Fixed: 809515