Devices/Device.py: Fix for broken cleanup() with missing tc tool

If no tc utility is present on the agent system, exec_cmd() raises an
exception. If uncaught, the previous address flush request will also not
complete. The address remaining in place will cause an EEXIST error upon
next test run, requiring manual intervention to resolve the situation.

Fixes: 49e523d ("Slave: Add basic support for tc.")
Signed-off-by: Phil Sutter <psutter@redhat.com>

lnst/Devices/Device.py

@@ -422,8 +422,11 @@ def cleanup(self):
 
         self.down()
         self.ip_flush()
-        self._clear_tc_qdisc()
-        self._clear_tc_filters()
+        try:
+            self._clear_tc_qdisc()
+            self._clear_tc_filters()
+        except ExecCmdFail:
+            pass
 
         self.restore_original_data()