Copying linked graphic between components is broken

IsLinkedGraphic() is better to use here.

Reproducer steps:
-Insert an image to Impress as a link.
-Copy this image (CTRL+C & CTRL+V) to Writer.
Result: Image is not displayed.

Change-Id: Iaf9b686b5c87caf5a0cc15425f8c5988f857bfe6
(cherry picked from commit 3650b66c366177877d30f6aae83a33bf683d3457)
Reviewed-on: https://gerrit.libreoffice.org/13609
Reviewed-by: Miklos Vajna <vmiklos@collabora.co.uk>
Tested-by: Miklos Vajna <vmiklos@collabora.co.uk>