Virgo data has no default NDS server

Created by: areeda

PLUS there's a typo in the warning format string I think

/Users/areeda/py_envs/gwpy/lib/python2.7/site-packages/gwpy/io/nds2.py:269: UserWarning: No default host found for ifo 'V'1
  warnings.warn('No default host found for ifo %r' % ifo)