This is particularly important for higher number of segments, but even
with small numbers there is a significant difference. For instance,
with 4 segments the fourth segment had no IPs assigned with the old
code, no matter how large the pool, because none of the eight bits used
for the segment check hashed/mapped to it.
If the provider has access to the full pool list, it can enumerate
them twice, for example to search for existing leases first, and
only search for new leases in a second step.
Fixes lease enumeration in attr-sql using multiple pools.
Tobias Brunner