Fix stub function fake_generate_ip for unit test
Fix stub function fake_generate_ip for unit test

1.What is the problem:
Neutron has just added one more parameter in _generate_ip function,
but there is no this parameter the stub function fake_generate_ip in
Tricircle plugin, this will lead to the Tricircle unit test failed.

2.What's need to be fixed:
In tricircle/tests/unit/network/test_plugin.py
update "def fake_generate_ip(context, subnets):" to
"def fake_generate_ip(context, subnets, prefer_next=False):"

3.What is the purpose of this patch set:
To make the Tricircle adapt to the change of Neutron so that the unit
test of the Tricircle could be exceuted successfully.

Change-Id: Ie715e3956f3ec7d3e3e4aedcd8b5e1c12c4df7ea
Signed-off-by: Chaoyi Huang <a9255ab284bb421be02744591ccbe1d599fb05d5@huawei.com>

stackforge/tricircle,stackforge/tricircle,openstack/tricircle,openstack/tricircle