Don't pop notifications for serviceunavailable errors.

app/src/main/java/at/bitfire/davdroid/syncadapter/CalendarsSyncAdapterService.java

@@ -79,6 +79,9 @@ public class CalendarsSyncAdapterService extends SyncAdapterService {
                     CalendarSyncManager syncManager = new CalendarSyncManager(getContext(), account, settings, extras, authority, syncResult, calendar, principal);
                     syncManager.performSync();
                 }
+            } catch (Exceptions.ServiceUnavailableException e) {
+                syncResult.stats.numIoExceptions++;
+                syncResult.delayUntil = (e.retryAfter > 0) ? e.retryAfter : Constants.DEFAULT_RETRY_DELAY;
             } catch (Exception | OutOfMemoryError e) {
                 if (e instanceof CalendarStorageException || e instanceof SQLiteException) {
                     App.log.log(Level.SEVERE, "Couldn't prepare local calendars", e);

app/src/main/java/at/bitfire/davdroid/syncadapter/ContactsSyncAdapterService.java

@@ -80,6 +80,9 @@ public class ContactsSyncAdapterService extends SyncAdapterService {
                     }
                 } else
                     App.log.info("No CardDAV service found in DB");
+            } catch (Exceptions.ServiceUnavailableException e) {
+                syncResult.stats.numIoExceptions++;
+                syncResult.delayUntil = (e.retryAfter > 0) ? e.retryAfter : Constants.DEFAULT_RETRY_DELAY;
             } catch (Exception | OutOfMemoryError e) {
                 String syncPhase = SyncManager.SYNC_PHASE_JOURNALS;
                 String title = getContext().getString(R.string.sync_error_contacts, account.name);

app/src/main/java/at/bitfire/davdroid/syncadapter/SyncManager.java

@@ -183,6 +183,7 @@ abstract public class SyncManager {
             App.log.log(Level.WARNING, "I/O exception during sync, trying again later", e);
             syncResult.stats.numIoExceptions++;
         } catch (Exceptions.ServiceUnavailableException e) {
+            syncResult.stats.numIoExceptions++;
             syncResult.delayUntil = (e.retryAfter > 0) ? e.retryAfter : Constants.DEFAULT_RETRY_DELAY;
         } catch (InterruptedException e) {