Fix the issue that under some scenario stop_proposal_execution does not take effect

[kidkun]

fix for ticket
#184
Instead of canceling an ongoing analyzer process, the patch let the analyzer process finish but does not execute the proposal. The client will still get anticipated result of execution(just like set dryrun=true).

[efeg]

Thanks for the patch.
The issue #184 is about enabling cancellation of an ongoing goal optimization, whereas this patch does not cancel once a thread is in the process of optimizing goals. Goal optimization is an expensive operation of the Analyzer module -- this is what we would like to cancel.

Moreover, setting _stopRequested.set(false); via the proposed ready() call would potentially prevent a user's stopExecution to take effect (please note the race condition when there is an ongoing execution, the user calls stop execution, then a second user calls any execution operation such as demote).

[kidkun]

close this one for now, plan to have a more comprehensive solution after the UUID feature get brought in(to have a better way to track the ongoing jobs).