code: boolean isMissingMember(Address address, String uuid) {
          Map<Object, MemberImpl> m = missingMembersRef.get();
          return isHotRestartEnabled() ? m.containsKey(uuid) : m.containsKey(address);
      }
docs: Returns whether member with given identity (either {@code UUID} or {@code Address}
  depending on Hot Restart is enabled or not) is a known missing member or not.
  
  @param address Address of the missing member
  @param uuid Uuid of the missing member
  @return true if it's a known missing member, false otherwise