Fix tools/burnin w.r.t. OpCreateInstance.ip_check

Since we added a new, required parameter to OpCreateInstance, we need to
update burnin to build the correct opcode.

Reviewed-by: schreiberal

tools/burnin

@@ -132,6 +132,7 @@ def BurninCluster(opts, args):
                                     os_type=opts.os, pnode=pnode,
                                     snode=snode, vcpus=1,
                                     start=True,
+                                    ip_check=True,
                                     wait_for_sync=True)
       Feedback("- Add instance %s on node %s" % (instance_name, pnode))
       result = proc.ExecOpCode(op, Feedback)