Test start/stop aliases in qa

This tests both that those two aliases have not been removed and also that
aliases handling hasn't been broken.

Reviewed-by: iustinp

qa/qa_instance.py

@@ -313,6 +313,13 @@ def _TestInstanceDiskFailure(instance, node, node2, onmaster):
   cmd = ['gnt-instance', 'startup', instance['name']]
   AssertEqual(StartSSH(master['primary'], sq(cmd)).wait(), 0)
 
+  # Verify that aliases have not been broken
+  cmd = ['gnt-instance', 'stop', instance['name']]
+  AssertEqual(StartSSH(master['primary'], sq(cmd)).wait(), 0)
+
+  cmd = ['gnt-instance', 'start', instance['name']]
+  AssertEqual(StartSSH(master['primary'], sq(cmd)).wait(), 0)
+
   cmd = ['gnt-cluster', 'verify']
   AssertEqual(StartSSH(master['primary'], sq(cmd)).wait(), 0)