If there are overlaps between the contents of two user
registries in the authentication chain (for example, where two user
registries both contain a user with the same user name), then the registry
that occurs earlier in the authentication chain will be given precedence.
This means that exactly the same order of precedence used during
authentication will be used during synchronization.
For example, if user A is queried from zone Z1 but already exists in SkyVault in zone Z2, then A is ignored if Z1 is later in the authentication chain than Z2.