[scripts] update cert tests to use thread_cert.TestCase (#4874)

- Update all test cases to inherit thread_cert.TestCase and update
  topologies accordingly. The topologies should all be correct because
  they are automatically generated, not hand written.

- Use default Thread version: 1.1

- Cleanup node tmp files in tmp directory according to the current
  PORT_OFFSET in setUp. This is required by
  test_reed_address_solicit_rejected.py and test_coap_observe.py since
  they define multiple test functions in one TestCase.

- Removed call to set_extaddr64 because it's not necessary and causing
  failures.

tests/scripts/thread-cert/Test_Cli.py

@@ -29,21 +29,15 @@
 
 import unittest
 
-import node
+import thread_cert
 
 LEADER = 1
 
 
-class Cert_Cli(unittest.TestCase):
-
-    def setUp(self):
-        self.nodes = {}
-        self.nodes[LEADER] = node.Node(LEADER)
-
-    def tearDown(self):
-        for n in list(self.nodes.values()):
-            n.stop()
-            n.destroy()
+class Cert_Cli(thread_cert.TestCase):
+    topology = {
+        LEADER: {},
+    }
 
     def test(self):
         commands = self.nodes[LEADER].get_commands()