This migrates the data in the server table to
the pool_attributes table. In addition, this
makes all the changes for the code to use the
nameserver pool_attribute in the default pool
instead of a server.
Paritally-implements: blueprint server-pools-storage
What's left to do:
- Remove the old server table and rest of the
server api code
Change-Id: I7e93ab53966cf71d7c8ced38fce55f76aec12e71