modemmonitor: use dbus-monitor

Instead of looping over mmcli commands to check for incoming
calls and texts every 3s, use dbus-monitor to tell us when
something is coming in.  This should save some battery life
as well as reduce the delay in new call/msg notification.

I was running on the latest released scripts, so have not
strictly tested this with git master.  Note that I dropped
the call to checkmissedcalls.  Perhaps we should still run
that at firststart?

Signed-off-by: Serge Hallyn <serge@hallyn.com>
Signed-off-by: Maarten van Gompel <proycon@anaproy.nl>

scripts/modem/sxmo_modemmonitor.sh

@@ -125,12 +125,16 @@ checkfornewtexts() {
 }
 
 mainloop() {
-	while true; do
-		checkformissedcalls
-		checkforincomingcalls
-		checkfornewtexts
-		sleep $TIMEOUT & wait
-	done
+	dbus-monitor --system "interface='org.freedesktop.ModemManager1.Modem.Voice',type='signal',member='CallAdded'" | \
+		while read line; do
+			checkforincomingcalls
+		done &
+	dbus-monitor --system "interface='org.freedesktop.ModemManager1.Modem.Messaging',type='signal',member='Added'" | \
+		while read line; do
+			checkfornewtexts
+		done &
+	wait
+	wait
 }
 
 mainloop