bug fix: Update genChangelog script

As the new Kimchi tags do not contain the "kimchi-" prefix, "git tag -l"
does not list the tags in the right order as it uses alphabetic order
and in genChangelog script we need creation order.
Fix it and also update ChangeLog file accordingly.

Signed-off-by: Aline Manera <alinefm@linux.vnet.ibm.com>