Member.toString clears highest bit of the id

[valepakh]

When looking at the logs that include string representation of the Member class, sometimes it's hard to detect differences because highest bit of the member id is cleared for some reason. We still use toHexString directly after that so there's no need to do that (if the initial intention was to see only positive values?) Example: Original UUID: 879162b5-0300-401a-9df3-18ca1f7df990 String representation: 79162b50300401a

[valepakh]

https://github.com/scalecube/scalecube-cluster/pull/401