vircgroup: Resolve Coverity RESOURCE_LEAK

Need to free 'root' and 'opts' before 'return -1' if symlink fails.
Signed-off-by: NWang Rui <moon.wangrui@huawei.com>

src/util/vircgroup.c

@@ -3757,7 +3757,7 @@ virCgroupIsolateMount(virCgroupPtr group, const char *oldroot,
                                      _("Unable to symlink directory %s to %s"),
                                      group->controllers[i].mountPoint,
                                      group->controllers[i].linkPoint);
-                return -1;
+                goto cleanup;
             }
         }
     }