QtIFW

Fix component selection shows wrong package sizes.

Task-number: QTIFW-302

This patch extends patch d4642f3ff. Reduce the number of calls
to calculate the uncompressed size to do it only once per model
update. We need to update the current selected component to
reflect possible sub-node changes.

Change-Id: I4a8121148f1974872b3c43d2f58351aad9c59421
Reviewed-by: Niels Weber <niels.weber@digia.com>
Reviewed-by: Karsten Heimrich <karsten.heimrich@digia.com>