Wifi: fix auto connect policy for forgetNetwork

Use shouldAutoConnect() to judge if Wi-Fi networks have to get
enabled.
Thus, after forget network, if shouldAutoConnect() is false,
do not enable other saved networks to prevent auto connect.

Change-Id: I05b00bba54876f2d0d928e0faa9476b8d51b84b4
CRs-Fixed: 684684