Removes unnecessary list handling from -c flag. (#659)

diff --git a/mobly/suite_runner.py b/mobly/suite_runner.py
index 83dca42..8e7eab0 100644
--- a/mobly/suite_runner.py
+++ b/mobly/suite_runner.py
@@ -57,7 +57,6 @@
     parser = argparse.ArgumentParser(description='Mobly Suite Executable.')
     parser.add_argument('-c',
                         '--config',
-                        nargs=1,
                         type=str,
                         required=True,
                         metavar='<PATH>',
@@ -73,7 +72,7 @@
         argv = sys.argv[1:]
     args = parser.parse_args(argv)
     # Load test config file.
-    test_configs = config_parser.load_test_config_file(args.config[0])
+    test_configs = config_parser.load_test_config_file(args.config)
 
     # Check the classes that were passed in
     for test_class in test_classes:
diff --git a/mobly/test_runner.py b/mobly/test_runner.py
index 05cd36b..84ddd34 100644
--- a/mobly/test_runner.py
+++ b/mobly/test_runner.py
@@ -64,7 +64,7 @@
         _print_test_names(test_class)
         sys.exit(0)
     # Load test config file.
-    test_configs = config_parser.load_test_config_file(args.config[0],
+    test_configs = config_parser.load_test_config_file(args.config,
                                                        args.test_bed)
     # Parse test specifiers if exist.
     tests = None
@@ -110,7 +110,6 @@
     group = parser.add_mutually_exclusive_group(required=True)
     group.add_argument('-c',
                        '--config',
-                       nargs=1,
                        type=str,
                        metavar='<PATH>',
                        help='Path to the test configuration file.')