IMS: Call forwarding icon should show after enable it.

If call forwarding is enabled, then the call forwarding
icon should be shown in notification bar.
Add a preference parameter to store the call forwarding
status, in case it is not updated in Icc records.
Move common functions into PhoneBase class.

Change-Id: I4da4bc78577dd10cd71563bc5f2dbfc3920416c7
CRs-Fixed: 795137