Fix unwanted data call deactivate when nonpreferred apn deleted

When a nonpreferred apn is deleted, deactivate data call is
triggered for active pdn.
Add check to trigger deactivate only when current apn setting is
not same as the preferred apn or when preferred apn is null.

Change-Id: Ie48fa9e22edda58aaa36694617d8bc66fbb768a2
Bug: 134372033