Fix error in address input format in "_ip_range_action_partial"

Fix error in address input format in "_ip_range_action_partial"

IP address format introduced in [1] should be unicode instead of string.
"ipaddress.IPv4Address(min_value)" doesn't parse correctly the input
parameter unless the parameter is in unicode format; this is valid both
for Python version 2 and 3.

Execution error if the parameter is a string:
>>> int(ipaddress.IPv4Address('10.0.3.2'))
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/local/lib/python2.7/dist-packages/ipaddress.py",
  line 1391, in __init__
    self._check_packed_address(address, 4)
  File "/usr/local/lib/python2.7/dist-packages/ipaddress.py",
  line 554, in _check_packed_address
    expected_len, self._version))
ipaddress.AddressValueError: '10.0.3.2' (len 8 != 4) is not permitted
as an IPv4 address. Did you pass in a bytes (str in Python 2) instead
of a unic

[1]https://github.com/opnfv/yardstick/blob/e5775e7efbc55f116b4d4ac11ff87b8d8553247e/yardstick/network_services/traffic_profile/traffic_profile.py#L87-L88

JIRA: YARDSTICK-996

Change-Id: Ic727a79044834b181c99789f0f5efc21c68f0ff2
Signed-off-by: Rodolfo Alonso Hernandez <rodolfo.alonso.hernandez@intel.com>