selftests/tc-testing: add exit code

Mark the summary result as FAIL to prevent from confusing the selftest
framework if some of them are failed.

Previously, the selftest framework always treats it as *ok* even though
some of them are failed actually. That's because the script tdc.sh always
return 0.

# All test results:
#
# 1..97
# ok 1 83be - Create FQ-PIE with invalid number of flows
# ok 2 8b6e - Create RED with no flags
[...snip]
# ok 6 5f15 - Create RED with flags ECN, harddrop
# ok 7 53e8 - Create RED with flags ECN, nodrop
# ok 8 d091 - Fail to create RED with only nodrop flag
# ok 9 af8e - Create RED with flags ECN, nodrop, harddrop
# not ok 10 ce7d - Add mq Qdisc to multi-queue device (4 queues)
# Could not match regex pattern. Verify command output:
# qdisc mq 1: root
# qdisc fq_codel 0: parent 1:4 limit 10240p flows 1024 quantum 1514 target 5ms interval 100ms memory_limit 32Mb ecn drop_batch 64
# qdisc fq_codel 0: parent 1:3 limit 10240p flows 1024 quantum 1514 target 5ms interval 100ms memory_limit 32Mb ecn drop_batch 64
[...snip]
# ok 96 6979 - Change quantum of a strict ETS band
# ok 97 9a7d - Change ETS strict band without quantum
#
#
#
#
ok 1 selftests: tc-testing: tdc.sh <<< summary result

CC: Philip Li <[e-mail]>
Reported-by: kernel test robot <[e-mail]>
Signed-off-by: Li Zhijian <[e-mail]>
Acked-by: Davide Caratti <[e-mail]>
Acked-by: Jamal Hadi Salim <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

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

···
         list_test_cases(alltests)
         exit(0)
 
+    exit_code = 0 # KSFT_PASS
     if len(alltests):
         req_plugins = pm.get_required_plugins(alltests)
         try:
···
             print('The following plugins were not found:')
             print('{}'.format(pde.missing_pg))
         catresults = test_runner(pm, args, alltests)
+        if catresults.count_failures() != 0:
+            exit_code = 1 # KSFT_FAIL
         if args.format == 'none':
             print('Test results output suppression requested\n')
         else:
···
                         gid=int(os.getenv('SUDO_GID')))
     else:
         print('No tests found\n')
+        exit_code = 4 # KSFT_SKIP
+    exit(exit_code)
 
 def main():
     """
···
         print('args is {}'.format(args))
 
     set_operation_mode(pm, parser, args, remaining)
-
-    exit(0)
-
 
 if __name__ == "__main__":
     main()