Bug 884486 Stored MCC matches nsIDOMMozMobileNetworkInfo r=daleharvey

Bug 828307 changed the type of the MCC in nsIDOMMozMobileNetworkInfo to
string.  Stored MCC values must also be of type string.

Change-Id: Idf861d2a372ffa4e428d9af3aa6439337a516e40
Merge pull request #10473 from mschwart/bug884486

Bug 884486 Stored MCC matches nsIDOMMozMobileNetworkInfo r=daleharvey