tc-testing: Clarify the use of tdc's -d option

  -v, --verbose         Show the commands that are being run

  -N, --notap           Suppress tap results for command under test

  -d DEVICE, --device DEVICE

                        Execute the test case in flower category

                        Execute test cases that use a physical device, where

                        DEVICE is its name. (If not defined, tests that require

                        a physical device will be skipped)

  -P, --pause           Pause execution just before post-suite stage

selection:

    time.sleep(2)

    for tidx in testlist:

        if "flower" in tidx["category"] and args.device == None:

            errmsg = "Tests using the DEV2 variable must define the name of a "

            errmsg += "physical NIC with the -d option when running tdc.\n"

            errmsg += "Test has been skipped."

            if args.verbose > 1:

                print('Not executing test {} {} because DEV2 not defined'.

                      format(tidx['id'], tidx['name']))

                print(errmsg)

            res = TestResult(tidx['id'], tidx['name'])

            res.set_result(ResultState.skip)

            res.set_errormsg('Not executed because DEV2 is not defined')

            res.set_errormsg(errmsg)

            tsr.add_resultdata(res)

            continue

        try:

        choices=['none', 'xunit', 'tap'],

        help='Specify the format for test results. (Default: TAP)')

    parser.add_argument('-d', '--device',

                        help='Execute the test case in flower category')

                        help='Execute test cases that use a physical device, ' +

                        'where DEVICE is its name. (If not defined, tests ' +

                        'that require a physical device will be skipped)')

    parser.add_argument(

        '-P', '--pause', action='store_true',

        help='Pause execution just before post-suite stage')