tc-testing: remove duplicate code in tdc.py

In set_operation_mode() function remove duplicated check for args.list
parameter, which is already done one line before.
Signed-off-by: NRoman Mashak <mrv@mojatatu.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

tools/testing/selftests/tc-testing/tdc.py

@@ -713,9 +713,8 @@ def set_operation_mode(pm, parser, args, remaining):
         exit(0)
 
     if args.list:
-        if args.list:
-            list_test_cases(alltests)
-            exit(0)
+        list_test_cases(alltests)
+        exit(0)
 
     if len(alltests):
         req_plugins = pm.get_required_plugins(alltests)