Fixup idea integration test to ignore ~/.pants.rc if present.

commit fe4d3517b998adf4f566c7e2a93bacff93ee1ee0
Author: John Sirois <jsirois@twitter.com>
Date:   Tue Aug 5 01:13:05 2014 -0600

    Fixup idea integration test to ignore ~/.pants.rc if present.

 tests/python/pants_test/tasks/test_idea_integration.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Testing Done:
Locally this used to fail for me with a customized ~/.pants.rc [idea]options, but now passes:
===
$ PANTS_DEV=1 ./pants goal test tests/python/pants_test/tasks/:idea_integration
...
01:15:51 00:00   [test]
01:15:51 00:00     [pytest]
01:15:51 00:00       [run]
                     ============== test session starts ===============
                     platform linux2 -- Python 2.6.9 -- py-1.4.23 -- pytest-2.6.0
                     plugins: cov, timeout
                     collected 8 items

                     tests/python/pants_test/tasks/test_idea_integration.py ........

                     =========== 8 passed in 17.78 seconds ============

01:16:10 00:19     [junit]
01:16:10 00:19     [specs]
               SUCCESS

Travis CI went green here: https://travis-ci.org/pantsbuild/pants/builds/31685448

Bugs closed: 441

Reviewed at https://rbcommons.com/s/twitter/r/828/