Before this patch endpoints were validated by container IP and port.
Depending on the endpoint controller logic neither of the two must match for a
valid endpoint (e.g. in a Mesos setup).
This patch checks that the endpoint targetRef points to the right pod by UID,
instead of comparing IPs.
A later patch will make sure the
compared port is the actual container port, not the host port.
/xref mesosphere/kubernetes-mesos#365
8848e26154