Enhance ceilometer statistics command with --period

Currently, if don't specify query parameter in ceilometer statistics
command, ceilometer statistics with --period will not work. This change
is trying to fix this issue.

Change-Id: I8723bad11d5c452c2834e33df9bb01ebdc6ce9ce
Fixs: bug #1202658

ceilometerclient/tests/v2/test_options.py

@@ -40,6 +40,15 @@ class BuildUrlTest(utils.BaseTestCase):
                                        'value': 43}])
         self.assertEqual(url, '/?q.op=&q.value=43&q.field=this')
 
+    def test_one_param(self):
+        url = options.build_url('/', None, ['period=60'])
+        self.assertEqual(url, '/?period=60')
+
+    def test_two_params(self):
+        url = options.build_url('/', None, ['period=60',
+                                            'others=value'])
+        self.assertEqual(url, '/?period=60&others=value')
+
 
 class CliTest(utils.BaseTestCase):
 

ceilometerclient/v2/options.py

@@ -39,7 +39,10 @@ def build_url(path, q, params=None):
         if params:
             for p in params:
                 path += '&%s' % p
-
+    elif params:
+        path += '?%s' % params[0]
+        for p in params[1:]:
+            path += '&%s' % p
     return path