Description of problem:

When attempting to use setxattr without a proper prefix (user, system, trusted, security), or no prefix,  it does not return an error.

Steps to reproduce:

with improper prefix:

$ python
>> vol = gfapi.Volume(<some server>,<some volume>)
>> vol.mount()
>> vol.setxattr('/tmp/test', 'a.test', 'value')

OR

with no prefix:

$ python
>> vol = gfapi.Volume(<some server>,<some volume>)
>> vol.mount()
>> vol.setxattr('/tmp/test', 'test', 'value')


Expected results:

Should throw proper error.