PR54587: LDAP connections used for authn were not respecting 
LDAPConnectionPoolTimeout due to confusion over what "bound" means.

Added some LDAP trace at TRACE5 to track how LDAP connections are
reused and rebound.



make LDAPConnectionPoolTTL more conservative, use r->request_time rather than
end-of-request time, and only update it after a round-trip with the LDAP
server rather than every time we check back into the pool.


Submitted by: covener
Reviewed/backported by: jim


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.4.x@1610396 13f79535-47bb-0310-9956-ffa450edef68