MAP: Synchronize notifcationReg reply and MNS connect action.

Use Case:
1. Connect to carkit
2. Disconnect connection with carkit.
3. Reconnect to carkit

Failure:
MNS Failure during Reconnection.
User will in some timing conditions not get notification
of new messages and then turns OFF/ON the carkit.
MAS is connected fine but for MNS car sends BAD REQUEST.

Root Cause:
This isssue is reported only with one particular carkit in MCE role,
where in MNS Connect request issued before acknowleding
the setNotificationReg Request.

Fix:
Synchronize handleRegistration method in handler thread to ensure
setNotificationReg response from MSE is sent before requesting
a MNS Connect to MCE.

Change-Id: I30559c643af7733754fce551b97e31543a0cb160