VCS: Simplify submit editor accept/close flow

* Replace message box with an error on the output pane.
* Separate logic for accept and close.

Change-Id: Ib9fa201a1a67ee195086f7a22bc6678a9642452a
Reviewed-by: Leena Miettinen <riitta-leena.miettinen@qt.io>
Reviewed-by: André Hartmann <aha_1980@gmx.de>

src/plugins/clearcase/clearcaseplugin.cpp

@@ -218,7 +218,7 @@ public:
 
 protected:
     void updateActions(VcsBase::VcsBasePluginPrivate::ActionState) override;
-    bool submitEditorAboutToClose() override;
+    bool activateCommit() override;
     void discardCommit() override { cleanCheckInMessageFile(); }
     QString ccGet(const FilePath &workingDir, const QString &file, const QString &prefix = {});
     QList<QStringPair> ccGetActivities() const;
@@ -734,7 +734,7 @@ ClearCasePluginPrivate::ClearCasePluginPrivate()
 }
 
 // called before closing the submit editor
-bool ClearCasePluginPrivate::submitEditorAboutToClose()
+bool ClearCasePluginPrivate::activateCommit()
 {
     if (!isCheckInEditorOpen())
         return true;