Reviewed by Adam Barth.

        commit-queue dies when test archiving fails
        https://bugs.webkit.org/show_bug.cgi?id=52617

        I looked at the machine and it had 10 archives already
        thus find_unused_name was returning None.  I've upped
        the limit to 100 (per bug) and tested the case where
        find_unused_name returns None (making archive return None).

        * Scripts/webkitpy/common/system/workspace.py:
        * Scripts/webkitpy/common/system/workspace_unittest.py:
        * Scripts/webkitpy/tool/bot/commitqueuetask.py:
        * Scripts/webkitpy/tool/bot/commitqueuetask_unittest.py:
        * Scripts/webkitpy/tool/commands/queues.py:

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@76071 268f45cc-cd09-0410-ab3c-d52691b4dbfc