Use None instead of mutables in method params default values

Mutables in the method params defaults might cause errors and
that's why it's anti-pattern in most of the cases and should be
removed.

Change-Id: Ib1498e68ab9cc770b237a324b733c85b4a5c6839

ceilometer/hardware/pollsters/util.py

@@ -41,8 +41,9 @@ def make_resource_metadata(res_metadata=None, host_url=None):
 
 def make_sample_from_host(host_url, name, sample_type, unit, volume,
                           project_id=None, user_id=None, resource_id=None,
-                          res_metadata=None, extra={}):
+                          res_metadata=None, extra=None):
 
+    extra = extra or {}
     resource_metadata = make_resource_metadata(res_metadata, host_url)
     resource_metadata.update(extra)
 

ceilometer/ipmi/platform/intel_node_manager.py

@@ -103,8 +103,10 @@ NM_GET_DEVICE_ID_TEMPLATE['Last_digit_firmware_build_number'] = 1
 NM_GET_DEVICE_ID_TEMPLATE['Image_flags'] = 1
 
 
-def _hex(list=[]):
+def _hex(list=None):
     """Format the return value in list into hex."""
+
+    list = list or []
     if list:
         list.reverse()
         return int(''.join(list), 16)

ceilometer/ipmi/platform/ipmitool.py

@@ -112,11 +112,14 @@ def _parse_output(output, template):
     return ret
 
 
-def execute_ipmi_cmd(template={}):
+def execute_ipmi_cmd(template=None):
     """Decorator for the execution of IPMI command.
 
     It parses the output of IPMI command into dictionary.
     """
+
+    template = template or []
+
     def _execute_ipmi_cmd(f):
         def _execute(self, **kwargs):
             args = ['ipmitool']

ceilometer/tests/api/v2/test_alarm_scenarios.py

@@ -628,9 +628,14 @@ class TestAlarms(v2.FunctionalTest,
             'not valid for this resource',
             resp.json['error_message']['faultstring'])
 
-    def _do_post_alarm_invalid_action(self, ok_actions=[], alarm_actions=[],
-                                      insufficient_data_actions=[],
+    def _do_post_alarm_invalid_action(self, ok_actions=None,
+                                      alarm_actions=None,
+                                      insufficient_data_actions=None,
                                       error_message=None):
+
+        ok_actions = ok_actions or []
+        alarm_actions = alarm_actions or []
+        insufficient_data_actions = insufficient_data_actions or []
         json = {
             'enabled': False,
             'name': 'added_alarm',