Made keepalived.conf template Chef 11 friendly

Fixes the following error in Chef 11:

Template Context:
-----------------
on line #25
 23: <% node['keepalived']['instances'].each_pair do |name, instance| -%>
 24: <%
 25:   instance['states'] ||= {}
 26:   instance['priorities'] ||= {}
 27:   instance['virtual_router_ids'] ||= {}

[2013-05-10T16:05:11-04:00] ERROR: Running exception handlers
[2013-05-10T16:05:11-04:00] FATAL: Saving node information to /var/chef/cache/failed-run-data.json
[2013-05-10T16:05:11-04:00] ERROR: Exception handlers complete
Chef Client failed. 1 resources updated
[2013-05-10T16:05:11-04:00] FATAL: Stacktrace dumped to /var/chef/cache/chef-stacktrace.out
[2013-05-10T16:05:11-04:00] FATAL: Chef::Mixin::Template::TemplateError: Node attributes are read-only when you do not specify which precedence level to set. To set an attribute use code like `node.default["key"] = "value"'