mesontest: Use setup timeout multiplier if not specified

The setup's timeout multiplier will always be set, and it will default
to 1.0, so just use that.

Without this, the setup's timeout multiplier was always ignored.

mesontest.py

@@ -83,7 +83,7 @@ def determine_worker_count():
                     help='Do not redirect stdout and stderr')
 parser.add_argument('-q', '--quiet', default=False, action='store_true',
                     help='Produce less output to the terminal.')
-parser.add_argument('-t', '--timeout-multiplier', type=float, default=1.0,
+parser.add_argument('-t', '--timeout-multiplier', type=float, default=None,
                     help='Define a multiplier for test timeout, for example '
                     ' when running tests in particular conditions they might take'
                     ' more time to execute.')
@@ -563,6 +563,8 @@ def run(args):
         global_env = merge_suite_options(options)
     else:
         global_env = build.EnvironmentVariables()
+        if options.timeout_multiplier is None:
+            options.timeout_multiplier = 1
 
     setattr(options, 'global_env', global_env)