This fixes bug 1008029.
The allocation is done as follows (according to the value of
port['fixed_ips']):
- api_router.ATTR_NOT_SPECIFIED - Quantum will generate an IP address.
If a v4 subnet is defined then a v4 address will be generated. If
a v6 subnet is defined then a v6 address will be generated. If both are
defined then both v4 and v6 addresses will be generated.
- user configuration which may contain a list of the following:
- ip_address - the specific IP address will be generated
- subnet_id - an IP address from the subnet will be generated
Change-Id: I3bb1b83b8824364b37dbecfa140331c4a1fd2762
80b9837857