Increase stablility of run-benchmark script

Increase stablility of run-benchmark script
https://bugs.webkit.org/show_bug.cgi?id=144361

Patch by Dewei Zhu <dewei_zhu@apple.com> on 2015-04-28
Reviewed by Ryosuke Niwa.

* Scripts/run-benchmark:
(main):
* Scripts/webkitpy/benchmark_runner/README.md: Update readme due to changes.
* Scripts/webkitpy/benchmark_runner/benchmark_builder/generic_benchmark_builder.py:
(GenericBenchmarkBuilder.clean):
* Scripts/webkitpy/benchmark_runner/benchmark_runner.py: Improve error handling and remove an unnecessary loop.
(BenchmarkRunner.__init__):
(BenchmarkRunner.execute):
* Scripts/webkitpy/benchmark_runner/browser_driver/osx_safari_driver.py:
(OSXSafariDriver.prepareEnv): Remove saved sessions of Safari.
* Scripts/webkitpy/benchmark_runner/data/patches/JetStream.patch: Upload 'results' rather than 'time'.
* Scripts/webkitpy/benchmark_runner/data/plans/jetstream.plan: Update formate.
* Scripts/webkitpy/benchmark_runner/data/plans/speedometer.plan: Update formate.
* Scripts/webkitpy/benchmark_runner/http_server_driver/http_server/twisted_http_server.py:
(ServerControl.render_POST): Flush the buffer to make sure we can pass the result to stdout.
* Scripts/webkitpy/benchmark_runner/http_server_driver/http_server_driver.py:
(HTTPServerDriver.fetchResult):
(HTTPServerDriver):
(HTTPServerDriver.killServer): Add kill server interface.
(HTTPServerDriver.getReturnCode): Add get return code interface.
* Scripts/webkitpy/benchmark_runner/http_server_driver/simple_http_server_driver.py: Adjust to support new interfaces.
(SimpleHTTPServerDriver.serve):
(SimpleHTTPServerDriver.fetchResult):
(SimpleHTTPServerDriver):
(SimpleHTTPServerDriver.killServer):
(SimpleHTTPServerDriver.getReturnCode):
* Scripts/webkitpy/benchmark_runner/utils.py:
(forceRemove): Provide python version of 'rm -rf'.

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@183520 268f45cc-cd09-0410-ab3c-d52691b4dbfc