Fix m_position value for compositions:

for compositions, in/out equal position in track, but
for clips, in/out equal in/out points from master clip unrelated to track position)

src/timeline2/model/compositionmodel.cpp

@@ -177,3 +177,9 @@ const QString &CompositionModel::displayName() const
 {
     return m_compositionName;
 }
+
+void CompositionModel::setInOut(int in, int out)
+{
+    m_position = in;
+    MoveableItem::setInOut(in, out);
+}

src/timeline2/model/compositionmodel.hpp

@@ -86,6 +86,7 @@ public:
 
 protected:
     Mlt::Transition *service() const override;
+    void setInOut(int in, int out) override;
 
     /* @brief Performs a resize of the given composition.
        Returns true if the operation succeeded, and otherwise nothing is modified

src/timeline2/model/moveableItem.hpp

@@ -109,7 +109,7 @@ protected:
     void setCurrentTrackId(int tid);
 
     /* Set in and out of service */
-    void setInOut(int in, int out);
+    virtual void setInOut(int in, int out);
 
 protected:
     std::weak_ptr<TimelineModel> m_parent;

src/timeline2/model/moveableItem.ipp

@@ -88,6 +88,5 @@ template <typename Service> void MoveableItem<Service>::setCurrentTrackId(int ti
 template <typename Service> void MoveableItem<Service>::setInOut(int in, int out)
 {
     QWriteLocker locker(&m_lock);
-    //m_position = in;
     service()->set_in_and_out(in, out);
 }