fix(link-cache): always bypass cache for dynamic links

Links created with a `null` address are allowed, as long as they
are also created with a dynamic `source`. In this cases we should
absolutely not cache the resultant link, as there is no other way
to differentiate the calls.

A test has also been added for the previously added `bypassCache`
functionality.

index.js

@@ -7,6 +7,12 @@ var ttl = 60000;
 var purgeTimeout = null;
 
 function createLink(address, options, type, method) {
+  if (address === null) {
+    // for the case of dynamically created links, we always want to bypass
+    // the link cache
+    return method(address, options);
+  }
+
   if (options && options.hasOwnProperty('bypassCache') && !!options.bypassCache) {
     return method(address, options);
   }

test/link-cache.test.js

@@ -57,4 +57,30 @@ describe('basic behavior', function() {
         });
     });
   });
+
+  it('should allow a user to bypass the link cache explicitly', function() {
+    return test.client.connect(config.address)
+      .then(function() {
+        return Promise.all([
+          test.client.createReceiver('amq.topic'),
+          test.client.createReceiver('amq.topic', { bypassCache: true })
+        ]);
+      })
+      .spread(function(link1, link2) {
+        expect(link1).to.not.eql(link2);
+      });
+  });
+
+  it('should bypass the cache for dynamic links', function() {
+    return test.client.connect(config.address)
+      .then(function() {
+        return Promise.all([
+          test.client.createReceiver(null, { attach: { source: { dynamic: true } } }),
+          test.client.createReceiver(null, { attach: { source: { dynamic: true } } })
+        ]);
+      })
+      .spread(function(link1, link2) {
+        expect(link1).to.not.eql(link2);
+      });
+  });
 });