android: set wantRunning to true when started from Always On VPN (#392)

This way, even if the VPN wasn't previously manually enabled, it'll still turn on after reboot

Updates #cleanup

Signed-off-by: Percy Wegmann <percy@tailscale.com>
(cherry picked from commit 46cdbb7b9b)

android/src/main/java/com/tailscale/ipn/IPNService.kt

@@ -39,9 +39,9 @@ open class IPNService : VpnService(), libtailscale.IPNService {
         }
         "android.net.VpnService" -> {
           // This means we were started by Android due to Always On VPN.
-          // Get the application to make sure it's been initialized, then
-          // request the VPN.
-          App.get()
+          // We don't show a foreground notification because we weren't
+          // started as a foreground service.
+          App.get().setWantRunning(true)
           Libtailscale.requestVPN(this)
           START_STICKY
         }