define priorities as a property on the test class

This is just cleaner than keeping a global dictionary.
diff --git a/tests/flow_query.py b/tests/flow_query.py
index 9931c89..cd607dd 100644
--- a/tests/flow_query.py
+++ b/tests/flow_query.py
@@ -83,9 +83,6 @@
 #@var fq_config Local copy of global configuration data
 fq_config = None
 
-# For test priority
-test_prio = {}
-
 
 def test_set_init(config):
     """
@@ -1691,7 +1688,6 @@
 
 # Disabled.
 # Should be DUT dependent.
-test_prio["Flow_Add_5_1"] = -1
 
 class Flow_Add_5_1(basic.SimpleProtocol):
     """
@@ -1700,6 +1696,8 @@
     INPUTS
     None
     """
+
+    priority = -1
     
     def runTest(self):
         logging.info("Flow_Add_5_1 TEST BEGIN")
@@ -1808,7 +1806,6 @@
 
 # Disabled because of bogus capacity reported by OVS.
 # Should be DUT dependent.
-test_prio["Flow_Add_6"] = -1
 
 class Flow_Add_6(basic.SimpleProtocol):
     """
@@ -1818,6 +1815,8 @@
     num_flows - Number of flows to generate
     """
 
+    priority = -1
+
     def runTest(self):
         logging.info("Flow_Add_6 TEST BEGIN")