Tests: Refactor tearDown show command logging, add lifecycle markers.

This change adds a consistent interface for adding test-specific show commands to
log.txt.

It also adds log markers for the execution of setUp[Class], tearDown[Class]
in the logs.

Change-Id: I7d42e396e594a59e866a7d55dac0af25548e657a
Signed-off-by: Paul Vinciguerra <pvinci@vinciconsulting.com>
diff --git a/test/test_classifier.py b/test/test_classifier.py
index 5144901..5b0eddb 100644
--- a/test/test_classifier.py
+++ b/test/test_classifier.py
@@ -75,10 +75,6 @@
     def tearDown(self):
         """Run standard test teardown and acl related log."""
         if not self.vpp_dead:
-            self.logger.info(self.vapi.ppcli("show inacl type ip4"))
-            self.logger.info(self.vapi.ppcli("show outacl type ip4"))
-            self.logger.info(self.vapi.cli("show classify table verbose"))
-            self.logger.info(self.vapi.cli("show ip fib"))
             if self.acl_active_table == 'ip_out':
                 self.output_acl_set_interface(
                     self.pg0, self.acl_tbl_idx.get(self.acl_active_table), 0)
@@ -93,6 +89,12 @@
 
         super(TestClassifier, self).tearDown()
 
+    def show_commands_at_teardown(self):
+        self.logger.info(self.vapi.ppcli("show inacl type ip4"))
+        self.logger.info(self.vapi.ppcli("show outacl type ip4"))
+        self.logger.info(self.vapi.cli("show classify table verbose"))
+        self.logger.info(self.vapi.cli("show ip fib"))
+
     def config_pbr_fib_entry(self, intf, is_add=1):
         """Configure fib entry to route traffic toward PBR VRF table