Do not check whether the apu_version.h file exists in the supplied APR-Util
location *twice*.  os.path.isfile(path) implicates os.path.exists(path), so
the second check effectively does nothing.

* build/generator/gen_win_dependencies.py
  (_find_apr_util_and_expat): Only check for the existence of the
    'apu_version.h' once.


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1603921 13f79535-47bb-0310-9956-ffa450edef68