A change introduced in Openfire 3.10.3 (OF-938) changed how the BOSH
implementation would add default namespace definitions where applicable.
This new implementation depends on a space from being present in the
outer stanza. The 'fin' element that's transmitted here is wrapped in
a message stanza without any attributes ( <message><fin ... ) which
caused the namespace to be injected in the fin element (where the first
space was).

This commit adds a 'to' attribute to the wrapping message stanza, to
allow for users to work around the problem without having to update
Openfire itself.

The BOSH implementation will be adjusted to account for this in another
commit.