don't use multistrap when building deb packages

We want to get system where we will build .deb packages. Since this commit
we will use docker image.

blueprint build-iso-on-fedora
Signed-off-by: Igor Gnatenko <ignatenko@mirantis.com>

Change-Id: I2f00b8be1bb04fe644a75827113fe2fdd1c38a21