Expect a missing directory, the asset cache is shared. Prevent spew if

two nodes run cleanup at the same time.

OpenSim/Region/CoreModules/Asset/FlotsamAssetCache.cs

@@ -588,6 +588,11 @@ namespace OpenSim.Region.CoreModules.Asset
                         dir, dirSize);
                 }
             }
+            catch (DirectoryNotFoundException)
+            {
+                // If we get here, another node on the same box has
+                // already removed the directory. Continue with next.
+            }
             catch (Exception e)
             {
                 m_log.Warn(