SSH Jobs should clear the StdOut and StdErr before start

current situation
SSH Jobs write to the stdOut and stdErr StringBuffers, but do not clear them.
Additionally the output from StdOut and StdErr is written to a Job/Order Parameter as well. That results in a second SSH Job will get the stdOut/Err of the first SSH Job and will get the job parameters, too.

desired behavior
When starting a SSH Job, the job parameters for StdOut/Err should get cleared.
When ending a SSH Job, the StringBuffers should be cleared.