[useradmin] Fix ensure_home_directory if path contains special character

[14/Aug/2018 14:47:51 -0700] middleware   INFO     Processing exception: 'ascii' codec can't decode byte 0xc3 in position 11: ordinal not in range(128): Traceback (most recent call last):
  File "/etc/lib/hue/build/env/lib/python2.7/site-packages/Django-1.6.10-py2.7.egg/django/core/handlers/base.py", line 112, in get_response
    response = wrapped_callback(request, *callback_args, **callback_kwargs)
  File "/etc/lib/hue/build/env/lib/python2.7/site-packages/Django-1.6.10-py2.7.egg/django/db/transaction.py", line 371, in inner
    return func(*args, **kwargs)
  File "/etc/lib/hue/apps/useradmin/src/useradmin/views.py", line 568, in add_ldap_users
    ensure_home_directory(request.fs, user)
  File "/etc/lib/hue/apps/useradmin/src/useradmin/views.py", line 803, in ensure_home_directory
    fs.do_as_user(username, fs.create_home_dir, home_directory)
  File "/etc/lib/hue/desktop/core/src/desktop/lib/fs/proxyfs.py", line 102, in do_as_user
    return fn(*args, **kwargs)
  File "/etc/lib/hue/desktop/core/src/desktop/lib/fs/proxyfs.py", line 171, in create_home_dir
    self._get_fs(home_path).create_home_dir(home_path)
  File "/etc/lib/hue/desktop/libs/hadoop/src/hadoop/fs/hadoopfs.py", line 247, in create_home_dir
    if not self.exists(home_path):
  File "/etc/lib/hue/desktop/libs/hadoop/src/hadoop/fs/webhdfs.py", line 297, in exists
    return self._stats(path) is not None
  File "/etc/lib/hue/desktop/libs/hadoop/src/hadoop/fs/webhdfs.py", line 281, in _stats
    return WebHdfsStat(json['FileStatus'], path)
  File "/etc/lib/hue/desktop/libs/hadoop/src/hadoop/fs/webhdfs_types.py", line 36, in __init__
    self.path = Hdfs.join(parent_path, self.name)
  File "/etc/lib/hue/desktop/libs/hadoop/src/hadoop/fs/hadoopfs.py", line 186, in join
    return posixpath.join(first, *comp_list)
  File "/etc/lib/hue/build/env/lib/python2.7/posixpath.py", line 73, in join
    path += '/' + b
UnicodeDecodeError: 'ascii' codec can't decode byte 0xc3 in position 11: ordinal not in range(128)