Re-enabled converation list observation while a conversation is open.

It honestly doesn't feel great to not have this, because when you back
out to the conversation list you have to wait for it to update.

Right now this seems like the lesser of two evils.

app/src/main/java/org/thoughtcrime/securesms/conversationlist/ConversationListFragment.java

@@ -320,7 +320,6 @@ public class ConversationListFragment extends MainFragment implements ActionMode
     super.onStart();
     ConversationFragment.prepare(requireContext());
     ApplicationDependencies.getAppForegroundObserver().addListener(appForegroundObserver);
-    viewModel.onStart();
   }
 
   @Override
@@ -336,7 +335,6 @@ public class ConversationListFragment extends MainFragment implements ActionMode
   public void onStop() {
     super.onStop();
     ApplicationDependencies.getAppForegroundObserver().removeListener(appForegroundObserver);
-    viewModel.onStop();
   }
 
   @Override

app/src/main/java/org/thoughtcrime/securesms/conversationlist/ConversationListViewModel.java

@@ -60,7 +60,6 @@ class ConversationListViewModel extends ViewModel {
   private String       activeQuery;
   private SearchResult activeSearchResult;
   private int          pinnedCount;
-  private boolean      isNewlyCreated;
 
   private ConversationListViewModel(@NonNull Application application, @NonNull SearchRepository searchRepository, boolean isArchived) {
     this.megaphone                = new MutableLiveData<>();
@@ -87,7 +86,6 @@ class ConversationListViewModel extends ViewModel {
         pagedData.getController().onDataInvalidated();
       });
     };
-    this.isNewlyCreated          = true;
 
     this.hasNoConversations = LiveDataUtil.mapAsync(pagedData.getData(), conversations -> {
       pinnedCount = DatabaseFactory.getThreadDatabase(application).getPinnedConversationListCount();
@@ -98,6 +96,8 @@ class ConversationListViewModel extends ViewModel {
         return DatabaseFactory.getThreadDatabase(application).getArchivedConversationListCount() == 0;
       }
     });
+
+    ApplicationDependencies.getDatabaseObserver().registerConversationListObserver(observer);
   }
 
   public LiveData<Boolean> hasNoConversations() {
@@ -142,20 +142,6 @@ class ConversationListViewModel extends ViewModel {
     coldStart = false;
   }
 
-  void onStart() {
-    if (!isNewlyCreated) {
-      pagedData.getController().onDataInvalidated();
-    }
-
-    isNewlyCreated = false;
-
-    ApplicationDependencies.getDatabaseObserver().registerConversationListObserver(observer);
-  }
-
-  void onStop() {
-    ApplicationDependencies.getDatabaseObserver().unregisterObserver(observer);
-  }
-
   void onMegaphoneCompleted(@NonNull Megaphones.Event event) {
     megaphone.postValue(null);
     megaphoneRepository.markFinished(event);