Use fast compression in test deb builds

Use fast compression in test deb builds

Builds on GCE/ubuntu image were taking a long time due to combination of
disk speed/single core, and the default dpkg-deb compression level
(-z9). The dpkg-deb alone step was taking up to 5 minutes. Reduce to ~1
minute by forcing -z1. Unfortunately, it was not obvious how to capture
the option in debuild command, so this is a bit hacky.

Signed-off-by: Brenden Blanco <bblanco@gmail.com>