Remove code in gsutil that removes http_proxy from the env var

Remove code in gsutil that removes http_proxy from the env var

boto config does the right thing by using the http_proxy env var to set the proxy,
and gsutil removes that var which isn't the behavior we want.
This should allow gsutil to respect the http_proxy env var.

BUG=318478
Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=235818

[Ryan Tseng, 2013-11-14 22:12:50]

+maruel review because, depot_tools change.

Not entirely sure how to test this without launching a squid proxy and a web
server.

[M-A Ruel, 2013-11-14 22:50:47]

rubberstamp lgtm

[commit-bot: I haz the power, 2013-11-14 22:53:30]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/hinoka@chromium.org/68763013/1

[commit-bot: I haz the power, 2013-11-14 22:55:07]

Presubmit check for 68763013-1 failed and returned exit status 1.

Running presubmit commit checks ...
Checking out rietveld...
Running save-description-on-failure.sh
Running push-basic.sh
Running upstream.sh
Running submit-from-new-dir.sh
Running abandon.sh
Running submodule-merge-test.sh
Running upload-local-tracking-branch.sh
Running hooks.sh
Running post-dcommit-hook-test.sh
Running upload-stale.sh
Running patch.sh
Running basic.sh

** Presubmit ERRORS **
tests/scm_unittest.py failed
...EEEE..........
======================================================================
ERROR: testGetGetSha1ForSvnRev (__main__.RealGitSvnTest)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "tests/scm_unittest.py", line 144, in setUp
    self.enabled = self.FAKE_REPOS.set_up_git() and self.FAKE_REPOS.set_up_svn()
  File
"/b/commit-queue/workdir/tools/depot_tools/testing_support/fake_repos.py", line
382, in set_up_git
    self.check_port_is_free(self.git_port)
  File
"/b/commit-queue/workdir/tools/depot_tools/testing_support/fake_repos.py", line
427, in check_port_is_free
    assert False, '%d shouldn\'t be bound' % port
AssertionError: 20000 shouldn't be bound

======================================================================
ERROR: testGetGitSvnHeadRev (__main__.RealGitSvnTest)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "tests/scm_unittest.py", line 144, in setUp
    self.enabled = self.FAKE_REPOS.set_up_git() and self.FAKE_REPOS.set_up_svn()
  File
"/b/commit-queue/workdir/tools/depot_tools/testing_support/fake_repos.py", line
362, in set_up_git
    assert self.git_pid_file == None
AssertionError

======================================================================
ERROR: testParseGitSvnSha1 (__main__.RealGitSvnTest)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "tests/scm_unittest.py", line 144, in setUp
    self.enabled = self.FAKE_REPOS.set_up_git() and self.FAKE_REPOS.set_up_svn()
  File
"/b/commit-queue/workdir/tools/depot_tools/testing_support/fake_repos.py", line
362, in set_up_git
    assert self.git_pid_file == None
AssertionError

======================================================================
ERROR: testIsValidRevision (__main__.RealGitTest)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "tests/scm_unittest.py", line 125, in setUp
    self.enabled = self.FAKE_REPOS.set_up_git()
  File
"/b/commit-queue/workdir/tools/depot_tools/testing_support/fake_repos.py", line
362, in set_up_git
    assert self.git_pid_file == None
AssertionError

----------------------------------------------------------------------
Ran 17 tests in 14.305s

FAILED (errors=4)


Presubmit checks took 94.4s to calculate.

[commit-bot: I haz the power, 2013-11-18 21:25:26]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/hinoka@chromium.org/68763013/1

[commit-bot: I haz the power, 2013-11-18 21:27:02]

Change committed as 235818