Fix for the mail subject if Ohai failed to set FQDN

Use node.ipaddress instead of node.fqdn if fqdn is not set.
Sometimes Ohai fails to set fqdn for the node. A couple of bugs are open for that.

Example below:

Running handlers:\x1b[0m
[2014-05-08T15:06:57-04:00] ERROR: Running exception handlers
[2014-05-08T15:06:57-04:00] ERROR: Report handler MailHandler raised #<NoMethodError: Undefined method or attribute `fqdn\' on `node\'>
[2014-05-08T15:06:57-04:00] ERROR: /opt/chef/embedded/lib/ruby/gems/1.9.1/gems/chef-11.12.4/lib/chef/node/attribute.rb:358:in `method_missing\'
[2014-05-08T15:06:57-04:00] ERROR: /opt/chef/embedded/lib/ruby/gems/1.9.1/gems/chef-11.12.4/lib/chef/node.rb:237:in `method_missing\'
[2014-05-08T15:06:57-04:00] ERROR: /opt/chef/embedded/lib/ruby/gems/1.9.1/gems/chef-handler-mail-0.1.2/lib/chef/handler/mail.rb:33:in `report\'
[2014-05-08T15:06:57-04:00] ERROR: /opt/chef/embedded/lib/ruby/gems/1.9.1/gems/chef-11.12.4/lib/chef/handler.rb:226:in `run_report_unsafe\'
[2014-05-08T15:06:57-04:00] ERROR: /opt/chef/embedded/lib/ruby/gems/1.9.1/gems/chef-11.12.4/lib/chef/handler.rb:214:in `run_report_safely\'
[2014-05-08T15:06:57-04:00] ERROR: /opt/chef/embedded/lib/ruby/gems/1.9.1/gems/chef-11.12.4/lib/chef/handler.rb:118:in `block in run_exception_handlers\'
[2014-05-08T15:06:57-04:00] ERROR: /opt/chef/embedded/lib/ruby/gems/1.9.1/gems/chef-11.12.4/lib/chef/handler.rb:117:in `each\'
[2014-05-08T15:06:57-04:00] ERROR: /opt/chef/embedded/lib/ruby/gems/1.9.1/gems/chef-11.12.4/lib/chef/handler.rb:117:in `run_exception_handlers\'
[2014-05-08T15:06:57-04:00] ERROR: /opt/chef/embedded/lib/ruby/gems/1.9.1/gems/chef-11.12.4/lib/chef/handler.rb:127:in `block in <class:Handler>\'
[2014-05-08T15:06:57-04:00] ERROR: /opt/chef/embedded/lib/ruby/gems/1.9.1/gems/chef-11.12.4/lib/chef/client.rb:133:in `call\'
[2014-05-08T15:06:57-04:00] ERROR: /opt/chef/embedded/lib/ruby/gems/1.9.1/gems/chef-11.12.4/lib/chef/client.rb:133:in `block in run_failed\'
[2014-05-08T15:06:57-04:00] ERROR: /opt/chef/embedded/lib/ruby/gems/1.9.1/gems/chef-11.12.4/lib/chef/client.rb:132:in `each\'
[2014-05-08T15:06:57-04:00] ERROR: /opt/chef/embedded/lib/ruby/gems/1.9.1/gems/chef-11.12.4/lib/chef/client.rb:132:in `run_failed\'
[2014-05-08T15:06:57-04:00] ERROR: /opt/chef/embedded/lib/ruby/gems/1.9.1/gems/chef-11.12.4/lib/chef/client.rb:447:in `rescue in do_run\'
[2014-05-08T15:06:57-04:00] ERROR: /opt/chef/embedded/lib/ruby/gems/1.9.1/gems/chef-11.12.4/lib/chef/client.rb:459:in `do_run\'
[2014-05-08T15:06:57-04:00] ERROR: /opt/chef/embedded/lib/ruby/gems/1.9.1/gems/chef-11.12.4/lib/chef/client.rb:213:in `block in run\'
[2014-05-08T15:06:57-04:00] ERROR: /opt/chef/embedded/lib/ruby/gems/1.9.1/gems/chef-11.12.4/lib/chef/client.rb:207:in `fork\'
[2014-05-08T15:06:57-04:00] ERROR: /opt/chef/embedded/lib/ruby/gems/1.9.1/gems/chef-11.12.4/lib/chef/client.rb:207:in `run\'
[2014-05-08T15:06:57-04:00] ERROR: /opt/chef/embedded/lib/ruby/gems/1.9.1/gems/chef-11.12.4/lib/chef/application.rb:217:in `run_chef_client\'
[2014-05-08T15:06:57-04:00] ERROR: /opt/chef/embedded/lib/ruby/gems/1.9.1/gems/chef-11.12.4/lib/chef/application/client.rb:328:in `block in run_application\'
[2014-05-08T15:06:57-04:00] ERROR: /opt/chef/embedded/lib/ruby/gems/1.9.1/gems/chef-11.12.4/lib/chef/application/client.rb:317:in `loop\'
[2014-05-08T15:06:57-04:00] ERROR: /opt/chef/embedded/lib/ruby/gems/1.9.1/gems/chef-11.12.4/lib/chef/application/client.rb:317:in `run_application\'
[2014-05-08T15:06:57-04:00] ERROR: /opt/chef/embedded/lib/ruby/gems/1.9.1/gems/chef-11.12.4/lib/chef/application.rb:67:in `run\'
[2014-05-08T15:06:57-04:00] ERROR: /opt/chef/embedded/lib/ruby/gems/1.9.1/gems/chef-11.12.4/bin/chef-client:26:in `<top (required)>\'
[2014-05-08T15:06:57-04:00] ERROR: /usr/bin/chef-client:23:in `load\'