tweak the referral/hoplimit ldap option logic to save the failure reason in the util_...

tweak the referral/hoplimit ldap option logic to save the failure reason in the util_ldap_connection_t for later logging

old error log message:
  auth_ldap authenticate: user wbush authentication failed; URI /ldap-status [(null)][Can't contact LDAP server]
new error log message:
  auth_ldap authenticate: user wbush authentication failed; URI /ldap-status [Unable to set LDAP_OPT_REFHOPLIMIT.][Can't contact LDAP server]

git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@735068 13f79535-47bb-0310-9956-ffa450edef68