[Forward-port to 10.2/trunk] HippoHtmlAdapter does not rewrite html links

org.onehippo.cms7.essentials.components.rest.adapters.HippoHtmlAdapter#marshal does not rewrite internal links correctly.

In this line the html.getNode().getParent() must be replaced with html.getNode().

final String rewrite = contentRewriter.rewrite(html.getContent(), html.getNode().getParent(), context, context.getResolvedMount().getMount());

Reproduction path:

• install project with 3.0.1 archetype
• add a content feature, e.g. News or Events
• in the CMS: add an internal link in the rich text field from one document to another
• use the Rest Services set up tool to create a rest service
• rebuild, restart
• retrieve the REST output of the service
• the href of the link is /site/pagenotfound