Vcs: Dissolve VcsManager::registerVersionControl

It's a somewhat unusual pattern, spelling it out will help
to move the vcs plugins setup closer to the now-usual pattern.

Change-Id: Ie7b70e52d75e34cd36b6a1d55ca868e3edab44a7
Reviewed-by: Orgad Shaneh <orgads@gmail.com>

src/plugins/clearcase/clearcaseplugin.cpp

@@ -411,7 +411,8 @@ bool ClearCasePlugin::initialize(const QStringList & /*arguments */, QString *er
 
     Context context(CLEARCASE_CONTEXT);
 
-    initializeVcs<ClearCaseControl>(context, this);
+    auto vcsCtrl = new ClearCaseControl(this);
+    initializeVcs(vcsCtrl, context);
 
     m_clearcasePluginInstance = this;
     connect(ICore::instance(), &ICore::coreAboutToClose, this, &ClearCasePlugin::closing);