Return True if path is a physical device.

def _is_device(path):
    '''
    Return True if path is a physical device.
    '''
    out = __salt__['cmd.run_all']('file -i {0}'.format(path))
    _verify_run(out)

    # Always [device, mime, charset]. See (file --help)
    return re.split(r'\s+', out['stdout'])[1][:-1] == 'inode/blockdevice'