[rilmodem] Notify core always about GPRS connection changes

After this change ofono core will be always notified if the gprs
connection status is different than before. This enables faster
recovery when moving between network technologies.

Signed-off-by: Jussi Kangas <jussi.kangas@oss.tieto.com>
Merge pull request #70 from jkangas/master

Request for pulling more detailed informing of the packet data status in rilmodem to main branch