Repair entitytreemodeltest which requires the itemsFetched private slot.

FakeAkonadiServerCommand::connectForwardingSignals() connects to it.

Not fully passing though, but much better than before...
FAIL!  : EntityTreeModelTest::testInitialFetch() Compared lists differ at index 0.
   Actual   (extractModelColumn(*m_model, parent, topLeft.row(), bottomRight.row())): QVariant(QString,Col 6)
   Expected (expectedSignal.newData): QVariant(QString,Col 2)
   Loc: [akonadi/autotests/libs/modelspy.cpp(84)]
FAIL!  : EntityTreeModelTest::testInitialFetch() Compared lists differ at index 0.
   Actual   (extractModelColumn(*m_model, parent, topLeft.row(), bottomRight.row())): QVariant(QString,Col 2)
   Expected (expectedSignal.newData): QVariant(QString,Col 7)
   Loc: [akonadi/autotests/libs/modelspy.cpp(84)]
FAIL!  : EntityTreeModelTest::testInitialFetch() Compared lists differ at index 0.
   Actual   (extractModelColumn(*m_model, parent, topLeft.row(), bottomRight.row())): QVariant(QString,Col 7)
   Expected (expectedSignal.newData): QVariant(QString,Col 6)
   Loc: [akonadi/autotests/libs/modelspy.cpp(84)]
Seems like an ordering problem...