Fix errors in xvfb.py and run_test_from_archive.py

Fix errors in xvfb.py and run_test_from_archive.py

run_test_from_archive_smoke_test.py didn't test directory creation so this was
broken. I tested it manually and weeded out the current bug.

For the modification in test_env.py, this is concerning. Without this
modification, I was getting:
Traceback (most recent call last):
  File "../testing/xvfb.py", line 133, in <module>
    sys.exit(main())
  File "../testing/xvfb.py", line 129, in main
    return run_executable(sys.argv[2:], sys.argv[1], os.environ.copy())
  File "../testing/xvfb.py", line 118, in run_executable
    return test_env.run_executable(cmd, env)
AttributeError: 'module' object has no attribute 'run_executable'

Adding a print() or anything else fixed the problem. I'm not sure what's
corrupted on my system.

TBR=cmp@chromium.org,csharp@chromium.org
NOTRY=true
BUG=


Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=153847

[commit-bot: I haz the power, 2012-08-29 03:50:52]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/maruel@chromium.org/10890027/1

[commit-bot: I haz the power, 2012-08-29 03:51:23]

Change committed as 153847

[M-A Ruel, 2012-08-29 03:52:11]

Also reduced logging.

[csharp, 2012-08-29 13:33:17]

lgtm

[cmp, 2012-08-29 21:05:55]

lgtm