add a static method to retrieve the LDAP errno, and call from a

few other paths that have us returning LDAP_OTHER (since
only 'server down' is retryable, we want to work hard to get
it returned when appropriate)


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@1157677 13f79535-47bb-0310-9956-ffa450edef68