Call DetectCountry only once per call

In current implementation detectCountry method is called from telephon
as many times as 34 for one MO voice call, causing increasing delay
to appear incallui for user.  This fix ensures that there is only one
call to detectCountry method per one voice call thus optimizing delay.

Change-Id: Ia6e832476c7f7be2750f1c2d9a4c83f728c2131e
CRs-Fixed: 803069