Fix *86 converting issue.

Our design is to convert *86 to +1MDN, using real MDN to replace string 'MDN'.
When phone roaming in GSM/UMTS network, MDN is grabbed from sim card's EF_MSISDN,
here the EF_MSISDN is +1XXXXX, so after converting, the number is changed to
+1+1XXXXX, and finally the second + and following part will be removed in
number format checking.

Bug: 17822591
Change-Id: Iafa0f36c4e58e80d3fd300a2a1430147332f4a1a