Use method from parent for set test context

Author: slawekjaranowski

maven-plugin-testing-harness/src/main/java/org/apache/maven/api/plugin/testing/MojoExtension.java

@@ -135,9 +135,8 @@ public void beforeEach(ExtensionContext context) throws Exception {
                 .map(Basedir::value)
                 .orElse(getBasedir());
         field.set(null, basedir);
-        field = PlexusExtension.class.getDeclaredField("context");
-        field.setAccessible(true);
-        field.set(this, context);
+
+        setContext(context);
 
         getContainer().addComponent(getContainer(), PlexusContainer.class.getName());