Vendor in latest containers/image

Adds support for credential helpers

Signed-off-by: umohnani8 <umohnani@redhat.com>

vendor/github.com/docker/docker-credential-helpers/osxkeychain/url_go18.go

@@ -0,0 +1,13 @@
+//+build go1.8
+
+package osxkeychain
+
+import "net/url"
+
+func getHostname(u *url.URL) string {
+	return u.Hostname()
+}
+
+func getPort(u *url.URL) string {
+	return u.Port()
+}