line_protocol: handle py2/py3 difference in _get_unicode().
line_protocol: handle py2/py3 difference in _get_unicode().

Fix test_make_lines_unicode() test. _get_unicode() with flag fails
under py27 if tag contains unicode.

influxdb/influxdb-python,influxdb/influxdb-python,Asimmetric/influxdb-python,influxdata/influxdb-python,wx00/influxdb-python,tzonghao/influxdb-python,BenHewins/influxdb-python,omki2005/influxdb-python,wx00/influxdb-python,BenHewins/influxdb-python,tzonghao/influxdb-python,influxdata/influxdb-python,omki2005/influxdb-python,Asimmetric/influxdb-python