Convert system/core to Result::ok()

No functionality changes, this is a mechanical cleanup.

Test: m
Test: cd system/core && atest
Change-Id: Ifdaa3ce1947ed578f656d5a446978726eb416c36
diff --git a/init/util.cpp b/init/util.cpp
index 0ca0da5..503c705 100644
--- a/init/util.cpp
+++ b/init/util.cpp
@@ -497,14 +497,14 @@
                 break;
             case 3:
                 uid = DecodeUid(args[3]);
-                if (!uid) {
+                if (!uid.ok()) {
                     return Error()
                            << "Unable to decode UID for '" << args[3] << "': " << uid.error();
                 }
                 break;
             case 4:
                 gid = DecodeUid(args[4]);
-                if (!gid) {
+                if (!gid.ok()) {
                     return Error()
                            << "Unable to decode GID for '" << args[4] << "': " << gid.error();
                 }