mod_delegation: use clean_xmlns to remove jabber:client namespace from node: for the same reason as in mod_privilege, `jabber:client` namespace is removed with the clean_xmlns method coming from there. Furthermore, the forwarded <iq> stanza use the `jabber:client` xmlns while the stanza may come from a component with e.g. `jabber:component:accept` xmlns, this can lead to inconsistencies between the <iq> stanza and children (like <error> element).

---
summary: STARTTLS failure test
---

This module responds to `<starttls xmlns='urn:ietf:params:xml:ns:xmpp-tls'/>` with
`<failure xmlns='urn:ietf:params:xml:ns:xmpp-tls'/>`, in order to test
how clients and server behave.

See [RFC6120 Section 5.4.2.2](https://xmpp.org/rfcs/rfc6120.html#rfc.section.5.4.2.2)