r18504: Handle mappings for RENAME and KEEP attributes better. We don't need

r18504: Handle mappings for RENAME and KEEP attributes better.  We don't need
to mess with the values in these cases.

Where we do convert the values, try and convert substrings.  This
isn't going to be perfect, but we should try rather than segfault.

This also avoids using the wrong arm of the union for the attribute
name

The change in the entryUUID module is to correct the case of
sAMAccountName, due to the case sensitive ldap.js test.

Andrew Bartlett
(This used to be commit 81d9a692c1e74ec9078bf718003eafdba85b4324)