plugins: Don't exit on duplicate plugin (#28390) (#28430)

* plugins: Don't exit on duplicate plugin

Signed-off-by: Arve Knudsen <arve.knudsen@gmail.com>

* Add missing files

Signed-off-by: Arve Knudsen <arve.knudsen@gmail.com>

* Fix test

Signed-off-by: Arve Knudsen <arve.knudsen@gmail.com>
(cherry picked from commit 4084b53f91)

Co-authored-by: Arve Knudsen <arve.knudsen@gmail.com>

pkg/plugins/plugins.go

@@ -271,6 +271,12 @@ func (pm *PluginManager) scan(pluginDir string, requireSigned bool) error {
 
 		// Load the full plugin, and add it to manager
 		if err := loader.Load(jsonParser, plugin, scanner.backendPluginManager); err != nil {
+			if errors.Is(err, duplicatePluginError{}) {
+				pm.log.Warn("Plugin is duplicate", "error", err)
+				scanner.errors = append(scanner.errors, err)
+				continue
+			}
+
 			return err
 		}