Increase maxIdleConnection limit when creating etcd client in apiserver.

[wojtek-t]

Fix #7160

cc @fgrzadkowski @lavalamp @xiang90

[fgrzadkowski]

lgtm.

[fgrzadkowski]

Will merge on green

[xiang90]

lgtm

[lavalamp]

:( Unfortunately, that means it needs to be located in a file in third_party

[wojtek-t]

Where exactly I should move it?

[lavalamp]

make a new directory/file in ``third_party/forked//.go` and make it a public function there. Also include the third party LICENSE and any header at the top of the file.

[wojtek-t]

Sorry for my ignorance here - but what should LICENCE file contain?
Any of files under Godeps/_workspace/src/github.com/coreos/go-etcd/etcd doesn't contain any licence-related header.

[lavalamp]

In that case, don't put the license or the header in. :)

[lavalamp]

@sillsm to verify that I'm recalling the instructions correctly...

[wojtek-t]

Done.

[lavalamp]

I really wanted to merge this but we should probably keep the lawyercats happy.

[wojtek-t]

PTAL

[wojtek-t]

@lavalamp I hope that the current directory structure is fine - if not please let me know.

[lavalamp]

LGTM

[smarterclayton]

Rather than forking this, it might be easier to reuse our existing TLS transport options:

    transport, err := client.TransportFor(&client.Config{
        TLSClientConfig: client.TLSClientConfig{
            CertFile: etcdClientInfo.ClientCert.CertFile,
            KeyFile:  etcdClientInfo.ClientCert.KeyFile,
            CAFile:   etcdClientInfo.CA,
        },
        WrapTransport: func(rt http.RoundTripper) http.RoundTripper {
            transport := rt.(*http.Transport)
            dialer := &net.Dialer{
                Timeout: 30 * time.Second,
                // Lower the keep alive for connections.
                KeepAlive: 1 * time.Second,
            }
            // Because watches are very bursty, defends against long delays
            // in watch reconnections.
            transport.MaxIdleConnsPerHost = 500
            transport.Dial = dialer.Dial
            return transport
        },
    })
    etcdClient := etcdclient.NewClient(etcdClientInfo.URLs)
    etcdClient.SetTransport(transport.(*http.Transport))