test: Run Alpine tests without network (#5220)

None of the unit tests should be reaching out to the network.
Since Alpine tests run under LXD, we can still easily run tests there
without network.

Also, include the tzdata package that was missed in 725f5fb and
remove unneeded network debug lines.

.github/workflows/alpine-unittests.yml

@@ -46,7 +46,7 @@ jobs:
           lxc exec alpine -- ping -c 1 dl-cdn.alpinelinux.org || true
 
       - name: Install dependencies
-        run: lxc exec alpine -- apk add py3-tox git
+        run: lxc exec alpine -- apk add py3-tox git tzdata
 
       - name: Mount source into container directory
         run: lxc config device add alpine gitdir disk source=$(pwd) path=/root/cloud-init-ro
@@ -60,5 +60,13 @@ jobs:
         # https://github.com/canonical/cloud-init/issues/5158
         run: lxc exec alpine -- ln -s /usr/share/zoneinfo/Europe/Brussels /etc/localtime
 
+      - name: Set up tox environment
+        # Setup the environment and then tell pytest to do essentially nothing
+        run: lxc exec alpine --cwd /root/cloud-init-rw -- tox -e py3 -- --cache-show=
+
+      - name: Stop network
+        # Take down network interfaces to ensure tests don't use network
+        run: lxc exec alpine -- ifdown -a
+
       - name: Run unittests
-        run: lxc exec alpine --cwd /root/cloud-init-rw -- sh -c "tox -e py3"
+        run: lxc exec alpine --cwd /root/cloud-init-rw -- tox -e py3