Error replacing URI path elements when element names overlap

[gdavison]

When replacing URI path elements using the function encoding/httpbinding.replacePathElement, if a later path element's name is a substring of a previous element, e.g. /{namespace}/{name}, it will fail with the following error:

serialization failed: invalid path element, does not contain token stop, /{namespace}/{name}

This does not happen if the substring occurs earlier in the URI, e.g. /{name}/{namespace}.

To reproduce, add the following test cases to TestPathReplace:

{
	Orig:       []byte("/{namespace}/{name}"),
	ExpPath:    []byte("/{namespace}/value"),
	ExpRawPath: []byte("/{namespace}/value"),
	Key:        "name", Val: "value",
},
{
	Orig:       []byte("/{name}/{namespace}"),
	ExpPath:    []byte("/value/{namespace}"),
	ExpRawPath: []byte("/value/{namespace}"),
	Key:        "name", Val: "value",
},

The first case will fail with

expected no error, got invalid path element, does not contain token stop, /{namespace}/{name}