exec enable cmd ignore ignore some apiservices error

[huiwq1990]

What this PR does / why we need it:

When execute command kubefedctl enable clusterrole，if some apiservices have error（like v1alpha1.wardle.example.com）, command will fail. We could ignore the error if apiserver has the resource, just like kubectl api-resource return data and error.

[root@tpaas ~]# kubectl get apiservice
NAME                                   SERVICE      AVAILABLE                  AGE
v1alpha1.scheduling.kubefed.io         Local        True                       2d3h
v1alpha1.wardle.example.com            wardle/api   False (MissingEndpoints)   67m
v1beta1.admissionregistration.k8s.io   Local        True                       3d23h


[root@tpaas ~]# kubefedctl enable clusterrole
F1230 00:12:28.599723    5416 enable.go:111] Error: Error listing api resources: unable to retrieve the complete list of server APIs: wardle.example.com/v1alpha1: the server is currently unable to handle the request

Which issue(s) this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close the issue(s) when PR gets merged):
Fixes #

Special notes for your reviewer:

[huiwq1990]

/assign @hectorj2f

[hectorj2f]

@huiwq1990 I'll have a look to your PR today.

[hectorj2f]

/lgtm

[k8s-ci-robot]

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This pull-request has been approved by: hectorj2f, huiwq1990

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