Add option to tune test run retries after failure

This change adds the --retries option for having facility to tune the
number of test run retries after a failure. Previously, this value could
not be overridden and such behaviour was inconvenient while developing a
new test (when test often fails and is under debugging).

Closes #334

lib/options.py

@@ -205,6 +205,14 @@ def __init__(self):
                 2 x CPU count). -1 means everything running consistently
                 (single process). """)
 
+        parser.add_argument(
+                "-r", "--retries",
+                dest='retries_count',
+                default=env_int('TEST_RUN_RETRIES', 3),
+                type=int,
+                help="""The number of test run retries after a failure.
+                Default: ${TEST_RUN_RETRIES} or 3.""")
+
         parser.add_argument(
                 "--reproduce",
                 dest="reproduce",

lib/test_suite.py

@@ -46,7 +46,7 @@ class TestSuite:
     tests and other suite properties. The server is started once per
     suite."""
 
-    RETRIES_COUNT = 3
+    RETRIES_COUNT = Options().args.retries_count
 
     def get_multirun_conf(self, suite_path):
         conf_name = self.ini.get('config', None)