Move packages to env file and allow extras per distro.

Config/ProvisionTests/Dockerfiles/opensuse

@@ -4,7 +4,7 @@ FROM opensuse/tumbleweed
 
 RUN zypper -n refresh \
    && zypper -n dist-upgrade -y \
-   && zypper -n install -y git bash curl sudo which
+   && zypper -n install -y $PACKAGES $EXTRA_OPENSUSE
 
 COPY bin/main.sh /root/main.sh
 RUN chmod +x /root/main.sh