fix(header): fix header name case

Author: peteyycz

lib/providers/httpTransaction/wraps/http.Server.prototype.js

@@ -34,7 +34,7 @@ function wrapListener(listener, collector, config) {
 
     var requestId = headers['request-id'] || requestQuery;
 
-    mustCollect = headers['x-must-collect'];
+    mustCollect = headers['X-Must-Collect'];
 
     if (!requestId) {
       requestId = uuid.v1();
@@ -103,7 +103,7 @@ function wrapListener(listener, collector, config) {
 
       if (mustCollect) {
         debug('x-must-collect header has been set');
-        response.setHeader('x-must-collect', 1);
+        response.setHeader('X-Must-Collect', 1);
       }
 
       originalWriteHead.apply(response, arguments);