fixes update-alternatives for openjdk installs

I'm not sure how others are using this cookbook, but it's currently in attribute hell for me. The only way I can actually get an openjdk 7 install is if I run chef-client and supply it json on the command line specifically for java. This is obviously not ideal, and if you want to use this cookbook in something like AWS Opsworks you might have issue overriding versions inside recipes, etc.

These changes fix that, for the openjdk recipe.