r17542: In using ldb_map, I ran across some very odd behaviours when we search

r17542: In using ldb_map, I ran across some very odd behaviours when we search
for objectClass=xyz.  The code has been warning at me 'no
covert_operator set', and indeed this is the case.  (It then proceeds to
strip this as a search expression)

In this commit, I have implemented a convert_operator for objectClass,
by pretending it is a simple MAP_CONVERT operator for the search
requests.

I also have changed the logic for when we should bail out.  I can only
see reason to bail out on the search if we have both local and remote
trees.  How can a remote-only search be un-splittable?

Andrew Bartlett
(This used to be commit 656e58672c357121647a080400fcab4e5d30b46b)