Set roaming based on both data and voice.

In GSM network the data roaming (from +CGREG) and the voice roaming (from +CREG) could be different. Set GSM roaming based on both data and voice roaming status and set it true if either indicates roaming.

This solves the unwanted roaming billing issues and respects the download roaming setting in systemUpdater, DownloadProvider, and MMS downloader. For more details refer to bug 2052473.