improve test-deb-install

This PR adds support for using the DOCKER_BUILD_PKGS env var to
better help defining what packege to build. It also adds support
for the integration-daemon so we can run it as a bundle.

Signed-off-by: Paul Liljenberg <liljenberg.paul@gmail.com>

add directory test

Adds missing directory test. This helps verifying that
DOCKER_BUILD_PKGS is a directory and exists before continueing.

Signed-off-by: Paul Liljenberg <liljenberg.paul@gmail.com>

fix indent

Signed-off-by: Paul Liljenberg <liljenberg.paul@gmail.com>