DcTracker: Don't leave CMD_IS_PROVISIONING_APN dangling

Change I99344d89235b24689cde14335bf593099169ef0d exited the message
handler without a reply to the caller, leaving the singlethread queue
waiting for a reply and blocking other async tasks.

Change-Id: If12361c0037e9ca0662d720acfe55215924b67fd
Frameworks : Make sure a reply is sent when not provisioning default apn

Not doing so holds up the entire async executor service and breaks things like
loading icons in the share dialog. To reproduce :

Upon boot, take screenshot and click share in the notification.

Change-Id: I1b1443bfa42d62b99881e770c08f79ebe3673139