[DNS] PHP 5.3 warning fixes

I cleaned some stuff in hosting_dns module :

• Creating a zone configuration file is only required by the master ;
• Creating a host configuration file is only required by the dnsmasq service ;
• record_set method needs more checks on arguments ;

Another undefined index in dns.config.inc line 135

I have separated "php 5.3 warning fixes" in a new patch (you need to remove old patches before applying this one).

About other fixes, each services (Dnsmasq, Bind and Bind slave) have a specific classe inherited from provisionService_dns because they need differents configuration files:

• Dnsmasq needs to create server, zone and host configuration files
• Bind needs to create server and zone config files
• Bind slave needs to create server config files

However, functions create_host, create_zone aren't overloaded to do exactly the right work. Each services use the same general function who deals with warnings to do the work. I think create_zone() function in provisionService_dns_bind_slave() class was originaly wrote to pass the master server IP to config class before generating the config file. Now, the master server IP is recovered from the context in the config class ... I have reused this code to solve this issue. I have created an other issue about that #1118286: [DNS] Each services need specific function to create config files.

Yes I'm interested to maintain the DNS module. What exactly is this work ?

This patch solves all "php 5.3 warning" without changing the current design pattern.