Fix rusage

[tomgreen66]

This should fix an issues reported in issue #22 where with PBS Pro 12.2 and pbs-drmaa we can get the following error:

68275.server
Your job has been submitted with id 68275.server
Traceback (most recent call last):
  File "ex3.py", line 36, in <module>
    main()
  File "ex3.py", line 26, in main
    retval = s.wait(jobid, drmaa.Session.TIMEOUT_WAIT_FOREVER)
  File "/home/user/drmaa_example/test_git/drmaa/session.py", line 472, in wait
    res_usage = adapt_rusage(rusage)
  File "/home/user/drmaa_example/test_git/drmaa/helpers.py", line 238, in adapt_rusage
    k, v = attr.split('=')
ValueError: too many values to unpack

With fix then it correctly works.

68277.server
Your job has been submitted with id 68277.server
Job: 68277.server finished with status True
Job status = done
Cleaning up

[dan-blanchard]

👍 Thanks!