Revert r240528 to reapply r240460; Roll swarm_client @ f89de358c2.

Revert r240528 to reapply r240460; Roll swarm_client @ f89de358c2.

$ git log aab3a62beb..f89de358c2 --date=short --format="%ad %ae %s" | sed 's/@chromium\.org//'
2013-12-13 maruel Remove the ban on 'command' that are declared in included .isolate file.
2013-12-12 maruel Fix assert occurring on OSX due to already hardlinked files.
2013-12-11 ganetsky Create a .gitignore file and add *.pyc to it
2013-12-11 maruel Stop signalling swarming error on Windows file locking.
2013-12-11 maruel Ensure variables are decoded to unicode.
2013-12-06 maruel Rename --command-variable to --extra-variables.
2013-12-06 maruel Add real variable support and split --variable in 3 different flags.
2013-12-05 vadimsh Add 'offset' parameter to StorageApi.fetch(...) method.
2013-12-05 maruel Change log message to be clearer.
2013-12-05 vadimsh Support custom HTTP headers in net.url_open.
2013-12-03 vadimsh Remove urllib2 support.
2013-12-03 vadimsh Wait for Storage's internal threads to finish before exiting.
2013-12-03 vadimsh Fix swarming_smoke_test.py and isolateserver_test.py.

This commit is done manually, as the breakage caused by the last commit can't be
tested on the Try Server. This is because of the way
build/scripts/slave/runisolatedtest.py modifies the .isolated.state files.

R=vadimsh@chromium.org
BUG=

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=240882

[M-A Ruel, 2013-12-13 20:13:37]

This CL depends on https://codereview.chromium.org/101303005/ to be propagated
on the "Win Tests *" builders. It will be committed manually.

[Vadim Sh., 2013-12-13 20:42:09]

lgtm

[M-A Ruel, 2013-12-13 22:13:14]

On 2013/12/13 20:42:09, Vadim Sh. wrote:
> lgtm

I'll roll to f89de358c2 while at it. I think I'll wait tomorrow to commit. The
tree has really slow cycle times these days.

[M-A Ruel, 2013-12-16 13:53:24]

Committed patchset #2 manually as r240882 (presubmit successful).