distributed amuse xenon error

[ipelupessy]

see amusecode/amuse#149 and xenon-middleware/xenon#462 !

[ipelupessy]

my suspicion is that the ssh implementation (jsch?) version needs to be updated, since it fails when it tries to contact a new/recent system (latest fedora), and works with an old system (e.g. 10.04, albeit virtualized)