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/mount_namespace.cpp b/init/mount_namespace.cpp
index 1a474fb..0749fe3 100644
--- a/init/mount_namespace.cpp
+++ b/init/mount_namespace.cpp
@@ -141,12 +141,12 @@
         if (entry->d_type == DT_DIR) {
             const std::string apex_path = from_dir + "/" + entry->d_name;
             const auto apex_name = GetApexName(apex_path);
-            if (!apex_name) {
+            if (!apex_name.ok()) {
                 LOG(ERROR) << apex_path << " is not an APEX directory: " << apex_name.error();
                 continue;
             }
             const std::string mount_path = to_dir + "/" + (*apex_name);
-            if (auto result = MountDir(apex_path, mount_path); !result) {
+            if (auto result = MountDir(apex_path, mount_path); !result.ok()) {
                 return result;
             }
         }
@@ -168,7 +168,7 @@
     };
 
     for (const auto& dir : kBuiltinDirsForApexes) {
-        if (auto result = ActivateFlattenedApexesFrom(dir, kApexTop); !result) {
+        if (auto result = ActivateFlattenedApexesFrom(dir, kApexTop); !result.ok()) {
             LOG(ERROR) << result.error();
             return false;
         }
@@ -295,7 +295,7 @@
             return false;
         }
 
-        if (auto result = MountLinkerConfigForDefaultNamespace(); !result) {
+        if (auto result = MountLinkerConfigForDefaultNamespace(); !result.ok()) {
             LOG(ERROR) << result.error();
             return false;
         }