Optimize IncallUI delay for voice calls

In current implementation detectCountry method is called from telephony
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.

CRs-Fixed: 803069
Change-Id: Ia6e832476c7f7be2750f1c2d9a4c83f728c2131e