jobclient: bugfix: faster shutdown at campaign end

The JobClient currently waits a LONG time until it really shuts down
after not having reached the server in sendResultsToServer() (which is
unfortunately the by far most probable point in the code to determine
this):

 -  A different bug (fixed in the previous commit) provoked the
    situation that a (way) too large amount of jobs was fetched
    before.
 -  sendResult() (called after each experiment iteration) realized
    that CLIENT_JOB_REQUEST_SEC seconds are over, and tried to
    prematurely call home to send first results (without planning to
    get new jobs yet).
 -  If the server was gone (done, or aborted), connect in
    sendResultsToServer() failed after several retries and timeouts.
 -  All subsequent calls to sendResult() retried connecting to the
    server (again, with retries and timeouts), once for each remaining
    job.
 -  When all jobs were done, getParam() tries to connect a last time,
    finally telling the experiment that nobody's home.

This resulted in client shutdown times of up to four hours (for the
default CLIENT_JOB_LIMIT of 1000) after the campaign server
terminated.  This change solves the issue by not handing out new
(cached) jobs after the connect failed once, making the experiment
terminate quickly.

Change-Id: I0d8cb2e084d783aca74c51a503fa72eb2b2eb0b7

src/core/efw/JobClient.hpp

@@ -37,6 +37,8 @@ private:
 	std::deque<ExperimentData*> m_parameters;
 	std::deque<ExperimentData*> m_results;
 
+	bool m_connect_failed;
+
 	bool connectToServer();
 	bool sendResultsToServer();
 	FailControlMessage_Command tryToGetExperimentData(ExperimentData& exp);