title: TestNG priority annotation conflicts the sequential execution
body: <p>I have prioritized the methods for every class in TestNG framework.When i am running the suite. I see the Priority 1 method for each of the class getting triggered first followed by next priority for each of the classes. </p>
  
  <p>i also tried using "preserve-order="true">" in testing.xml but to dismay the issue is as is.</p>
  
  <p>..to elaborate</p>
  
  <pre><code>Class A
  {@Test(priority =1)
   method A1()
  @Test(priority =2)
   method A2}
  
  Class B
  {@Test(priority =1)
   method B1()
  @Test(priority =2)
   method B2}
  </code></pre>
  
  <p>When the suite is trigerred- Execution sequence is A1, B1, A2 and B2. For a similar scenario in the same project in a different package, i see the execution sequence A1, A2, B1 and B2</p>