tc-testing: Add newline when writing test case files

When using the -i feature to generate random ID numbers for test
cases in tdc, the function that writes the JSON to file doesn't
add a newline character to the end of the file, so we have to
add our own.

Signed-off-by: Lucas Bates <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

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

···
                     testlist.append(t)
         outfile = open(f, "w")
         json.dump(testlist, outfile, indent=4)
+        outfile.write("\n")
         outfile.close()
 
 def filter_tests_by_id(args, testlist):