Wifi: wifi not connecting, once the APN gets disabled state

APNs are disabled on select network and they are enabled on
receiving connected event. But forgetting an APN before the
connected event is received,will result all the remaining APN
to be in disabled state and they never connect.
So, Enabling all the disabled APN on forget network will help
to connect automatically to a saved APN.

Change-Id: I0aec08f118c3f33fceea60f5a6b44622717d93ed
CRs-fixed: 567655