nsd: retain query params in HTTP health checks (#17936)

Apply the same logic as Consul service health checks when building the
HTTP URL so that query params in `path` are preserved.

.changelog/17936.txt

@@ -0,0 +1,3 @@
+```release-note:bug
+services: Fixed a bug that prevented passing query parameters in Nomad native service discovery HTTP health check paths
+```

client/serviceregistration/checks/client.go

@@ -155,11 +155,18 @@ func (c *checker) checkHTTP(ctx context.Context, qc *QueryContext, q *Query) *st
 		return qr
 	}
 
-	u := (&url.URL{
+	relative, err := url.Parse(q.Path)
+	if err != nil {
+		qr.Output = err.Error()
+		qr.Status = structs.CheckFailure
+		return qr
+	}
+
+	base := url.URL{
 		Scheme: q.Protocol,
 		Host:   addr,
-		Path:   q.Path,
-	}).String()
+	}
+	u := base.ResolveReference(relative).String()
 
 	request, err := http.NewRequest(q.Method, u, nil)
 	if err != nil {

client/serviceregistration/checks/client_test.go

@@ -39,6 +39,19 @@ func TestChecker_Do_HTTP(t *testing.T) {
 
 	// create an http server with various responses
 	ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		// handle query param requests with string match because we want to
+		// test the path is set correctly instead of with escaped query params.
+		if strings.Contains(r.URL.Path, "query-param") {
+			if r.URL.RawQuery == "" {
+				w.WriteHeader(400)
+				_, _ = io.WriteString(w, "400 bad request")
+			} else {
+				w.WriteHeader(200)
+				_, _ = io.WriteString(w, "200 ok")
+			}
+			return
+		}
+
 		switch r.URL.Path {
 		case "/fail":
 			w.WriteHeader(http.StatusInternalServerError)
@@ -182,6 +195,16 @@ func TestChecker_Do_HTTP(t *testing.T) {
 			http.StatusCreated,
 			truncate,
 		),
+	}, {
+		name: "query param",
+		qc:   makeQueryContext(),
+		q:    makeQuery(structs.Healthiness, "query-param?a=b"),
+		expResult: makeExpResult(
+			structs.Healthiness,
+			structs.CheckSuccess,
+			http.StatusOK,
+			"nomad: http ok",
+		),
 	}}
 
 	for _, tc := range cases {