Small rewrite to ease debugging
Small rewrite to ease debugging

- Removed the locking on RuntimeDependency.is_valid() -> could cause dead lock
  (access of self.value should be protected with a specific lock)
- Replaced @SynchronizedClassMethod by "with lock" in some methods, to debug dead locks more easily

tcalmant/ipopo,ahmadshahwan/ipopo,ahmadshahwan/ipopo