[FIX] packaging: fix docker file for src tests

Since bf3193ac libsass is needed but is named libsass0 in Debian.
With this commit, the docker source image used for tests will build again.

setup/package.dfsrc

@@ -20,7 +20,7 @@ RUN apt-get update -qq &&  \
 		postgresql-server-dev-all \
 		postgresql-client \
 		adduser \
-		libsass \
+		libsass0 \
 		libxml2-dev \
 		libxslt1-dev \
 		libldap2-dev \