Fix issue that default dialer change is broadcasted unintentionally

With current code logic, whenever there is any role change, it is
marked as default dialer changed, as a result broadcast indicating
that the current default dialer has changed is sent unintentionally.

This patch adds new condition that only when the dialer role matches
then the broadcast is sent.

Test: Build and manual test on device.
Change-Id: Ie4f782ecf46c1e9e98747d731a4eecdb01041363
Signed-off-by: Wei Huang <hwbest.v@gmail.com>
Signed-off-by: Shu Wang <wangshu921978095@gmail.com>
Signed-off-by: Haoyu Luo <haoyu.luo1020@gmail.com>