https://bugs.webkit.org/show_bug.cgi?id=72677

Reviewed by Adam Barth.

Remove more uses of os.path, including refactoring
CommitterValidator to use a Host object instead of
manual hacks to emulate what SCM and FileSystem provide.

* Scripts/webkitpy/common/checkout/changelog.py:
* Scripts/webkitpy/common/config/committervalidator.py:
* Scripts/webkitpy/common/config/committervalidator_unittest.py:
* Scripts/webkitpy/common/system/filesystem_mock.py:
 - Turns out none of our unittests actually looked at this path.
   now I've made it be a valid path.
* Scripts/webkitpy/tool/bot/feeders.py:
* Scripts/webkitpy/tool/commands/queues.py:

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@100697 268f45cc-cd09-0410-ab3c-d52691b4dbfc