For v6_stateless IP addresses for all stateless
subnets within a network are implicitly included.
When using segments implicitly allocating addresses
across subnets on different segments is incorrect.
IPs from subnets on differnt segments was allocated
when no host binding information was available
but a subnet_id in fixed_ips request was present.
This change adds filtering based on segment_id when
fixed_ips are used. If fixed_ips are not all on the
same segment exception FixedIpsSubnetsNotOnSameSegment
is raised.
Related: rhbz#1803989
Related-Bug: #1864333
Related-Bug: #1865138
Closes-Bug: #1864225
Change-Id: I336ae76283f29dd226344fb454aaa0e4aac030ea
(cherry picked from commit 7e09e72661)