GPS: Disable XTRA data download at bootup to avoid service interaction

In Froyo mDownloadXtraDataPending is initialized to true resulting
in a unnecessary XTRA download attempted at bootup. This sometimes
causes a delay in the framework in responding to data connection
requests from the GPS engine when XTRA download fails. Hence XTRA
download at boot up is disabled with this fix. Normal XTRA data
requests from the modem will still be serviced by the framework.

Change-Id: Ib541b86de7731ae5f6938db79a9b6d5006b7ca52
CRs-Fixed:249425