Cleanup back-off alarm

app/src/main/java/eu/faircode/email/ServiceSynchronize.java

@@ -1220,6 +1220,7 @@ public class ServiceSynchronize extends LifecycleService {
                             registerReceiver(alarm, new IntentFilter(id));
 
                             AlarmManager am = getSystemService(AlarmManager.class);
+                            try {
                                 am.setAndAllowWhileIdle(
                                         AlarmManager.RTC_WAKEUP,
                                         System.currentTimeMillis() + CONNECT_BACKOFF_AlARM * 60 * 1000L,
@@ -1231,6 +1232,11 @@ public class ServiceSynchronize extends LifecycleService {
                                 } finally {
                                     wl0.acquire();
                                 }
+                            } finally {
+                                // Cleanup
+                                am.cancel(pi);
+                                unregisterReceiver(alarm);
+                            }
                         }
 
                         if (backoff < CONNECT_BACKOFF_MAX)