datajoint/jobs.py: use platform.node() for windows (fix for #470)

[ixcat]

Fix for #470.

Only tested against current unit tests on unix, which obviously is not a very good test in terms of completeness or correctness. Will hope to do a proper run on windows and also verify the jobs unit test covers the case (probably does, but not 100%), unless someone else feels more confident about impact.

Also, os.getpid() does work on windows; this was verified even if actual change was not otherwise.

[coveralls]

Coverage increased (+0.005%) to 89.294% when pulling 602a152 on ixcat:windows_jobs into fe5f749 on datajoint:master.

[coveralls]

Coverage increased (+0.005%) to 89.294% when pulling 602a152 on ixcat:windows_jobs into fe5f749 on datajoint:master.