test: Apply pasta hack to scenarios as well

Commit 9279fd4 didn't apply the hack to the "updates-testing"
and "podman-next" scenarios, as these *overwrite* `VM_CUSTOMIZE_FLAGS`
to get rid of the `--offline`.

Reorganize VM_CUSTOMIZE_FLAGS a bit to deal with `--no-network` in a
cleaner way.

Fixes #1611

Makefile

@@ -20,12 +20,22 @@ DIST_TEST=dist/manifest.json
 COCKPIT_REPO_STAMP=pkg/lib/cockpit-po-plugin.js
 # common arguments for tar, mostly to make the generated tarballs reproducible
 TAR_ARGS = --sort=name --mtime "@$(shell git show --no-patch --format='%at')" --mode=go=rX,u+rw,a-s --numeric-owner --owner=0 --group=0
-# default customize_flags
-VM_CUSTOMIZE_FLAGS = --no-network
+
+VM_CUSTOMIZE_FLAGS =
 
 # HACK: https://github.com/containers/podman/issues/21896
 VM_CUSTOMIZE_FLAGS += --run-command 'nmcli con add type dummy con-name fake ifname fake0 ip4 1.2.3.4/24 gw4 1.2.3.1 >&2'
 
+# the following scenarios need network access
+ifeq ("$(TEST_SCENARIO)","updates-testing")
+VM_CUSTOMIZE_FLAGS += --run-command 'dnf -y update --setopt=install_weak_deps=False --enablerepo=updates-testing >&2'
+else ifeq ("$(TEST_SCENARIO)","podman-next")
+VM_CUSTOMIZE_FLAGS = --run-command 'dnf -y copr enable rhcontainerbot/podman-next >&2; dnf -y update --repo "copr*" >&2'
+else
+# default scenario does not install packages
+VM_CUSTOMIZE_FLAGS += --no-network
+endif
+
 ifeq ($(TEST_COVERAGE),yes)
 RUN_TESTS_OPTIONS+=--coverage
 NODE_ENV=development
@@ -157,14 +167,6 @@ rpm: $(TARFILE)
 	find tmp/rpmbuild -name '*.rpm' -printf '%f\n' -exec mv {} . \;
 	rm -r tmp/rpmbuild
 
-ifeq ("$(TEST_SCENARIO)","updates-testing")
-VM_CUSTOMIZE_FLAGS = --run-command 'dnf -y update --setopt=install_weak_deps=False --enablerepo=updates-testing >&2'
-endif
-
-ifeq ("$(TEST_SCENARIO)","podman-next")
-VM_CUSTOMIZE_FLAGS = --run-command 'dnf -y copr enable rhcontainerbot/podman-next >&2; dnf -y update --repo "copr*" >&2'
-endif
-
 # build a VM with locally built distro pkgs installed
 $(VM_IMAGE): $(TARFILE) packaging/debian/rules packaging/debian/control packaging/arch/PKGBUILD bots
 	# HACK for ostree images: skip the rpm build/install