title: protractor: onPrepare for different test suites
body: <p>I have onPrepare in my conf.js file where I log in to the application.  My understanding is every time I run 1 or more test suites, it first executes whatever is in onPrepare.  This is great, as I use onPrepare to log into the application before running the tests.</p>
  
  <p>Issue is, I don't want to login when I run my login-spec.js suite.</p>
  
  <p>I could first logout before running through login-spec.js, but there must be a more elegant way to do this.</p>