Improved VH manifest alias tracking for packages without aliases.

I5c459bb092666088c3eedb33155bf06df75b6285 added an empty set of
aliases to all manifests including those that are actually aliases
this had the side effect of breaking the alias graph traversal.
This patch only adds an empty set of aliases to manifests who are
not aliases of other manifests.

Change-Id: I83a195c7f17864f0ce01e7e7a99d717ddeb631ce

Author: Stewart Miles

source/VersionHandlerImpl/src/VersionHandlerImpl.cs

@@ -1429,12 +1429,27 @@ private Dictionary<string, HashSet<string>> GetManifestAliasesByName() {
                         }
                         aliases.Add(metadata.customManifestNames.Values[0]);
                     }
+                }
+            }
+            // If manifest isn't an alias and doesn't have any aliases store an empty set.
+            foreach (var metadataByVersion in Values) {
+                var metadata = metadataByVersion.MostRecentVersion;
+                if (metadata.isManifest) {
+                    var manifestName = metadata.ManifestName;
+                    bool found = false;
+                    foreach (var kv in aliasesByName) {
+                        if (kv.Key == manifestName || kv.Value.Contains(manifestName)) {
+                            found = true;
+                            break;
+                        }
+                    }
                     // If there are no aliases, store an empty set.
-                    if (metadata.customManifestNames.Values.Count == 0) {
+                    if (!found) {
                         aliasesByName[metadata.ManifestName] = new HashSet<string>();
                     }
                 }
             }
+
             // Display adjacency list for debugging.
             var logLines = new List<string>();
             foreach (var nameAndAliases in aliasesByName) {