udev-test: make sure we run udev tests with selinux assumed off

This is cleaner that way given that we create our own half-virtualizes
device tree, and really shouldn't pull selinux labelling and access
control into that, we can only lose, in particular as our overmounted
/sys/ actually lacks /sys/fs/selinux.

(This fixes udev test woes introduced by #16821 where suddenly the test
would fail because libselinux assumed selinux was on, but selinuxfs
wasn't actually available)

src/test/meson.build

@@ -757,7 +757,8 @@ tests += [
           librt,
           libblkid,
           libkmod,
-          libacl],
+          libacl,
+          libselinux],
          '', 'manual', '-DLOG_REALM=LOG_REALM_UDEV'],
 
         [['src/test/test-id128.c'],

src/test/test-udev.c

@@ -71,6 +71,12 @@ static int run(int argc, char *argv[]) {
         if (r < 0)
                 return r;
 
+        /* Let's make sure the test runs with selinux assumed disabled. */
+#if HAVE_SELINUX
+        fini_selinuxmnt();
+#endif
+        mac_selinux_retest();
+
         if (argc == 2) {
                 if (!streq(argv[1], "check")) {
                         log_error("Unknown argument: %s", argv[1]);