Consolidate common code that got duplicated by 2.3.x authz refactoring.

Arrange for backend LDAP connections to be returned 
to the pool by a fixup hook rather than staying locked
until the end of (a potentially slow) request.

Add a little more trace4 to the authnz_ldap side of LDAP connection obtain/release.




git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@1608202 13f79535-47bb-0310-9956-ffa450edef68