Fix no endpoints issue when named ports are used

[aledbf]

fixes #839

[k8s-reviewable]

This change is 

[coveralls]

Coverage decreased (-0.05%) to 46.508% when pulling a970ef8 on aledbf:fix-named-ports into cdbf2aa on kubernetes:master.

[justinsb]

So I think the matching should be stricter - I put up #846 as my experimentation. Once we find the ServicePort on the Service object, the only way to match that to an EndpointPort is by Name. The only exception is that the ServicePort Name is optional if there is only one port, so in that case we match always.

At least I think so :-)