The DatastoreConfig discovery type is unused. Remove the constant and
any resulting dead code. Today's biggest loser is the IPAM Allocator:
DatastoreConfig was the only type of discovery event it was listening
for, and there was no other place where a non-nil datastore could be
passed into the allocator. Strip out all the dead persistence code from
Allocator, leaving it as purely an in-memory implementation.
There is no more need to check the consistency of the allocator's
bit-sequences as there is no persistent storage for inconsistent bit
sequences to be loaded from.
Signed-off-by: Cory Snider <csnider@mirantis.com>