Bugfix for GUC's values with units (#2883)

Despite being validated by `IntValidator` some GUC's couldn't be casted directly to `int` because they include suffix. Example: `128MB`.

Close https://github.com/zalando/patroni/issues/2879

patroni/config.py

@@ -490,7 +490,8 @@ class Config(object):
             elif not is_local:
                 validator = ConfigHandler.CMDLINE_OPTIONS[name][1]
                 if validator(value):
-                    pg_params[name] = int(value) if isinstance(validator, IntValidator) else value
+                    int_val = parse_int(value) if isinstance(validator, IntValidator) else None
+                    pg_params[name] = int_val if isinstance(int_val, int) else value
                 else:
                     logger.warning("postgresql parameter %s=%s failed validation, defaulting to %s",
                                    name, value, ConfigHandler.CMDLINE_OPTIONS[name][0])

tests/test_config.py

@@ -155,6 +155,7 @@ class TestConfig(unittest.TestCase):
         expected_params = {
             'f.oo': 'bar',  # not in ConfigHandler.CMDLINE_OPTIONS
             'max_connections': 100,  # IntValidator
+            'wal_keep_size': '128MB',  # IntValidator
             'wal_level': 'hot_standby',  # EnumValidator
         }
         input_params = deepcopy(expected_params)