Use more accurate description in service notification.

You are actually just connected to the VI - it may not be sending
anything.

openxc/res/values/strings.xml

@@ -1,7 +1,7 @@
 <?xml version="1.0" encoding="utf-8"?>
 <resources>
     <string name="openxc_name">OpenXC</string>
-    <string name="notification_content">Receiving vehicle data</string>
+    <string name="notification_content">Connected to vehicle</string>
 
     <string name="native_gps_checkbox_key">use_native_gps</string>
     <string name="gps_overwrite_checkbox_key">overwrite_native_gps</string>