test: check the skip condition before installing additional files

test/units/TEST-43-PRIVATEUSER-UNPRIV.sh

@@ -6,13 +6,13 @@ set -o pipefail
 # shellcheck source=test/units/util.sh
 . "$(dirname "$0")"/util.sh
 
-install_extension_images
-
 if [[ "$(sysctl -ne kernel.apparmor_restrict_unprivileged_userns)" -eq 1 ]]; then
     echo "Cannot create unprivileged user namespaces" >/skipped
     exit 77
 fi
 
+install_extension_images
+
 systemd-analyze log-level debug
 
 runas testuser systemd-run --wait --user --unit=test-private-users \