(ITS#7303) bdb/hdb search checks aliases unnecessarily

Full_Name: Howard Chu Version: HEAD/RE24 OS: URL: ftp://ftp.openldap.org/incoming/ Submission from: (NULL) (37.19.96.193) Submitted by: hyc

If a search request has derefSearching set in the alias deref option, the search_aliases() function walks thru a (potentially) large number of entries checking to see if they are aliases, even if the objectclass index shows there are no alias entries in the database. It should exit early instead.

The bug is also present to a lesser degree in back-mdb; the back-mdb version of search_aliases() would only do a single unneeded entry lookup.