core: Update go-cleanhttp vendored dependency

Updates go-cleanhttp vendored dependency

vendor/github.com/hashicorp/go-cleanhttp/cleanhttp.go

@@ -3,11 +3,12 @@ package cleanhttp
 import (
 	"net"
 	"net/http"
+	"runtime"
 	"time"
 )
 
-// DefaultTransport returns a new http.Transport with the same default values
-// as http.DefaultTransport, but with idle connections and keepalives disabled.
+// DefaultTransport returns a new http.Transport with similar default values to
+// http.DefaultTransport, but with idle connections and keepalives disabled.
 func DefaultTransport() *http.Transport {
 	transport := DefaultPooledTransport()
 	transport.DisableKeepAlives = true
@@ -22,13 +23,15 @@ func DefaultTransport() *http.Transport {
 func DefaultPooledTransport() *http.Transport {
 	transport := &http.Transport{
 		Proxy: http.ProxyFromEnvironment,
-		Dial: (&net.Dialer{
+		DialContext: (&net.Dialer{
 			Timeout:   30 * time.Second,
 			KeepAlive: 30 * time.Second,
-		}).Dial,
-		TLSHandshakeTimeout: 10 * time.Second,
-		DisableKeepAlives:   false,
-		MaxIdleConnsPerHost: 1,
+		}).DialContext,
+		MaxIdleConns:          100,
+		IdleConnTimeout:       90 * time.Second,
+		TLSHandshakeTimeout:   10 * time.Second,
+		ExpectContinueTimeout: 1 * time.Second,
+		MaxIdleConnsPerHost:   runtime.GOMAXPROCS(0) + 1,
 	}
 	return transport
 }
@@ -42,10 +45,10 @@ func DefaultClient() *http.Client {
 	}
 }
 
-// DefaultPooledClient returns a new http.Client with the same default values
-// as http.Client, but with a non-shared Transport. Do not use this function
-// for transient clients as it can leak file descriptors over time. Only use
-// this for clients that will be re-used for the same host(s).
+// DefaultPooledClient returns a new http.Client with similar default values to
+// http.Client, but with a shared Transport. Do not use this function for
+// transient clients as it can leak file descriptors over time. Only use this
+// for clients that will be re-used for the same host(s).
 func DefaultPooledClient() *http.Client {
 	return &http.Client{
 		Transport: DefaultPooledTransport(),

vendor/vendor.json

@@ -1639,9 +1639,10 @@
 			"revision": "e4b2dc34c0f698ee04750bf2035d8b9384233e1b"
 		},
 		{
-			"checksumSHA1": "fSe5y1UgTDeYlnFfUcDA1zzcw+U=",
+			"checksumSHA1": "b8F628srIitj5p7Y130xc9k0QWs=",
 			"path": "github.com/hashicorp/go-cleanhttp",
-			"revision": "875fb671b3ddc66f8e2f0acc33829c8cb989a38d"
+			"revision": "3573b8b52aa7b37b9358d966a898feb387f62437",
+			"revisionTime": "2017-02-11T01:34:15Z"
 		},
 		{
 			"checksumSHA1": "nsL2kI426RMuq1jw15e7igFqdIY=",