Bug 828633 - fix remote phone number parsing

After merging MultiSIM, remote phone number parsing should take last 5 digits rather than 4 ones. This causes all __remote_number_string_to_port()__ calls return a negative value meaning invalid remote number, and fails all remote phone number related functions like SMS loopback, etc. See [Bug 828633](https://bugzilla.mozilla.org/show_bug.cgi?id=828633).