Fix pickle-ability

- remove reference to 'sitelock' which was removed in
  I28435df24ef9faff929aceb2095e9fd97c66e33d
- keep _msgcache; it is not worth a separate set of methods just to remove it
- remove commented out code in tests

Change-Id: I689972e677118dec51d4d09e67eff422f75e2d87