Revert "tools/libxl: search PATH for QEMU if QEMU_XEN_PATH is not absolute"

This reverts commit f3ba5baf54, for
breaking the build in gitlab CI.

tools/libs/light/libxl_dm.c

@@ -331,43 +331,9 @@ const char *libxl__domain_device_model(libxl__gc *gc,
         case LIBXL_DEVICE_MODEL_VERSION_QEMU_XEN_TRADITIONAL:
             dm = libxl__abs_path(gc, "qemu-dm", libxl__private_bindir_path());
             break;
-        case LIBXL_DEVICE_MODEL_VERSION_QEMU_XEN: {
-            const char *configured_dm = qemu_xen_path(gc);
-            if (configured_dm[0] == '/')
-            {
-                dm = configured_dm;
-            }
-            else
-            {
-                const char *path_env = getenv("PATH");
-                if (!path_env)
-                {
-                    dm = configured_dm;
-                }
-                else
-                {
-                    char *path_dup = libxl__strdup(gc, path_env);
-                    char *saveptr;
-
-                    char *path = strtok_r(path_dup, ":", &saveptr);
-                    dm = NULL;
-                    while (path)
-                    {
-                        char *candidate = libxl__abs_path(gc, configured_dm, path);
-                        if (access(candidate, X_OK) == 0)
-                        {
-                            dm = candidate;
-                            break;
-                        }
-                        path = strtok_r(NULL, ":", &saveptr);
-                    }
-
-                    if (!dm)
-                        dm = configured_dm;
-                }
-            }
+        case LIBXL_DEVICE_MODEL_VERSION_QEMU_XEN:
+            dm = qemu_xen_path(gc);
             break;
-        }
         default:
             LOG(ERROR, "invalid device model version %d",
                 info->device_model_version);