tests/tpm-vm: use a shorter dev name on older LXD releases

Signed-off-by: Simon Deziel <simon.deziel@canonical.com>

tests/tpm-vm

@@ -46,6 +46,11 @@ lxc stop "${vmName}" --force
 # TPM names are included on the swtpm socket path and long socket paths can cause problems if not handled correctly.
 echo "==> Test handling TPMs with long names"
 longName="tpm-device-with-long-name-for-testing"
+# XXX: LXD releases 5.21 and earlier don't support long names (yet)
+if echo "${LXD_SNAP_CHANNEL}" | grep -E '^([45]\.0|5\.21)/'; then
+    echo "::warning::${LXD_SNAP_CHANNEL} detected, using a shorter name"
+    longName="notSoLongName"
+fi
 lxc config device add "${vmName}" "${longName}" tpm
 lxc start "${vmName}"
 waitInstanceReady "${vmName}"