test: make the test entrypoint scripts shellcheck-compliant

test/TEST-41-ONESHOT-RESTART/test.sh

@@ -1,6 +1,9 @@
 #!/usr/bin/env bash
 set -e
+
 TEST_DESCRIPTION="Test oneshot unit restart on failure"
-. $TEST_BASE_DIR/test-functions
+
+# shellcheck source=test/test-functions
+. "${TEST_BASE_DIR:?}/test-functions"
 
 do_test "$@" 41