Revert "specify a ResponseHeaderTimeout value"

This reverts commit 73ef9e2.

Setting timeout here may cause timeouts on uploading big layer blob.

Signed-off-by: Tonis Tiigi <tonistiigi@gmail.com>

Author: tonistiigi

util/resolver/resolver.go

@@ -206,7 +206,6 @@ func newDefaultTransport() *http.Transport {
 		MaxIdleConnsPerHost:   4,
 		TLSHandshakeTimeout:   10 * time.Second,
 		ExpectContinueTimeout: 5 * time.Second,
-		ResponseHeaderTimeout: 30 * time.Second,
 		TLSNextProto:          make(map[string]func(authority string, c *tls.Conn) http.RoundTripper),
 	}
 }