Revert "automatically guess the Debian-installer's kernel version"

Failed to build ISO with this commit:
http://jenkins-product.srt.mirantis.net:8080/view/6.0/job/6.0.iso/71/console

This reverts commit 41d9e60a6c347021ed8db18a637902ca524d020d.

Change-Id: Iad63c6b36e32abeb7923e205396459acc049c10b
Merge "Revert "automatically guess the Debian-installer's kernel version""