Improve setup of the schema cache location

1. Prevent from errors when the host is configured e.g. with ldap:// prefix
2. Use sys_get_temp_dir() to get the system tmp directory

lib/Net/LDAP3.php

@@ -2149,8 +2149,9 @@ class Net_LDAP3
             );
             $_ldap_schema_cache_cfg = array(
-                'path' => "/tmp/" . $host . ":" . ($port ? $port : '389') . "-Net_LDAP2_Schema.cache",
                 'max_age' => 86400,
+                'path' => sprintf('%s/%s:%d-Net_LDAP2_Schema.cache',
+                    (sys_get_temp_dir() ?: '/tmp'), str_replace('://', ':', $host) . (strpos($host, ":$port") ? '' : ":$port")),
             );
             $_ldap = Net_LDAP2::connect($_ldap_cfg);