(ITS#4518) better back-meta handling of search after failed connections

[ando@sys-net.it]

Full_Name: Pierangelo Masarati
Version: HEAD
OS: irrelevant
URL: ftp://ftp.openldap.org/incoming/
Submission from: (NULL) (81.72.89.40)
Submitted by: ando


In back-meta each subsearch is initiated before waiting for results.  Currently,
if one ldap_search() fails, that target is simply not considered for the
duration of that search.  This is consistent with back-meta design for most
errors; however, when a search is performed by back-meta after one target went
offline and came back, LDAP_SERVER_DOWN is returned.  A better approach for this
specific case consists in retrying the connection.

A fix is coming.