Upgrade/Install: Store correct result when bulk updating plugins or themes.

This ensures that when multiple plugins or themes are updated and one succeeds and another fails, the error is reported accordingly.

Previously, both updates would end up treated as a success, due to `$this->result` containing the result of the previous operation and not the current one.

Follow-up to [12097].

Props pwtyler, afragen.
Fixes #53002.

git-svn-id: https://develop.svn.wordpress.org/trunk@51528 602fd350-edb4-49c9-b593-d223f7449a82

Author: SergeyBiryukov

src/wp-admin/includes/class-plugin-upgrader.php

@@ -347,7 +347,7 @@ public function bulk_upgrade( $plugins, $args = array() ) {
 				)
 			);
 
-			$results[ $plugin ] = $this->result;
+			$results[ $plugin ] = $result;
 
 			// Prevent credentials auth screen from displaying multiple times.
 			if ( false === $result ) {

src/wp-admin/includes/class-theme-upgrader.php

@@ -448,7 +448,7 @@ public function bulk_upgrade( $themes, $args = array() ) {
 				)
 			);
 
-			$results[ $theme ] = $this->result;
+			$results[ $theme ] = $result;
 
 			// Prevent credentials auth screen from displaying multiple times.
 			if ( false === $result ) {