Endpoints generated by the endpoints controller are in the canonical
form, however, custom endpoints can not be in canonical format
(there was a time they were canonicalized in the apiserver, but this
caused performance issues because the endpoint controller kept
updating them since the created endpoint were different than the
stored one due to the canonicalization)
There are cases where a custom endpoint may generate multiple slices
due to the controller, per example, when the same address is present
in different subsets.
The endpointslice mirroring controller should canonicalize the
endpoints subsets before start processing them to be consistent
on the slices generated, there is no risk of hotlooping because
the endpoint is only used as input.
Change-Id: I2a8cd53c658a640aea559a88ce33e857fa98cc5c
ef6d9edea5