test/stub: add some call required by the next patches

As we use the new connection syntax in folderman.cpp, some more symbol
need to be mocked

test/stub.cpp

@@ -1,5 +1,7 @@
 // stub to prevent linker error
 #include "accountmanager.h"
-OCC::AccountManager *OCC::AccountManager::instance() { return 0; }
+OCC::AccountManager *OCC::AccountManager::instance() { return static_cast<AccountManager *>(new QObject); }
 void OCC::AccountManager::saveAccountState(AccountState *) { }
 void OCC::AccountManager::save(bool saveCredentials) { Q_UNUSED(saveCredentials); }
+void OCC::AccountManager::accountRemoved(OCC::AccountState*) { }
+const QMetaObject OCC::AccountManager::staticMetaObject = QObject::staticMetaObject;