Avoid magic number in success case of ldap search

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

Author: dzaporozhets

lib/net/ldap.rb

@@ -680,7 +680,7 @@ def search(args = {})
       if return_result_set
         unless @result.nil?
           case @result.result_code
-          when 0
+          when ResultStrings.key("Success")
             # everything good
             result_set
           when ResultStrings.key("Size Limit Exceeded")