Implement support for GCE health check with HTTP Host Header in GLBC

[itamaro]

Fixes issue #388 (for me, at least :-) )

[k8s-reviewable]

This change is 

[coveralls]

Coverage increased (+0.07%) to 46.199% when pulling c4dbc87 on itamaro:glbc-healthcheck-with-host-header into edb9b00 on kubernetes:master.

[nicksardo]

I'll look at this after 0.9.2 goes out. The flagset fix was small and harmless enough to include. Thanks.

Edit: See issue for comments

[nicksardo]

@itamaro Could you rebase this and fix it up? We were considering to use the node-level health check implemented in K8s 1.7.0, but have decided against that path. Thanks!

[coveralls]

Coverage increased (+0.02%) to 46.678% when pulling b6c1693 on itamaro:glbc-healthcheck-with-host-header into c6b5335 on kubernetes:master.

[itamaro]

@itamaro Could you rebase this and fix it up?

pushed an attempt. it seems much has changed since my initial attempt, so I'm not sure this is correct (and can't test it at the moment).

[nicksardo]

Thanks. Needs this line to use the correct host: https://github.com/kubernetes/ingress/blob/ca5f402322097b7fc079effaa2597eadae65734d/controllers/gce/backends/backends.go#L463 as you did in the previous commit.

I can make a new PR if you're too busy for this - didn't want to steal your work.

[itamaro]

something like the update I've pushed?

feel free to modify it, you should have write permissions :-)

[coveralls]

Coverage increased (+0.005%) to 44.592% when pulling 488dd07 on itamaro:glbc-healthcheck-with-host-header into ca5f402 on kubernetes:master.

[nicksardo]

/lgtm

Tested this and it worked fine. Thanks @itamaro!