ItemView cache should always be refreshed during scrolling

ItemView cache should always be refreshed during scrolling

[problem]      When ItemView is scrolling, activate a new layout and no new items are
               created.
[cause]        Caching extra items are avoided when activating new layout in order to
               improve the performance. However, new layout can be activated during
               scrolling, and no new items are created in that case.
[solution]     Always refresh the cache with extra items while scrolling.

Change-Id: I12a5810b2c35891d1928a9853a6ed1d21e1eada4
Signed-off-by: Adeel Kazmi <adeel.kazmi@samsung.com>