[lxd-import] github: purge disabled/superseded snaps

This is to reclaim some space.

Signed-off-by: Simon Deziel <simon.deziel@canonical.com>
(cherry picked from commit 875480ca306b421442bb7ebbce45ff2634b2cea8)

.github/workflows/tests.yml

@@ -214,6 +214,10 @@ jobs:
           sudo apt-get update
 
           sudo snap remove lxd --purge
+          # Purge older snap revisions that are disabled/superseded by newer revisions of the same snap
+          snap list --all | while read -r name _ rev _ _ notes _; do
+            [ "${notes}" = "disabled" ] && snap remove "${name}" --revision "${rev}" --purge
+          done || true
           sudo apt-get autopurge moby-containerd docker uidmap -y
           sudo ip link delete docker0
           sudo nft flush ruleset