Allow filtering of node collection

This patch adds filter method to NodeCollection
that allow filtering by ip, mac and fqdn.

Change-Id: Ida1f1fe62c4a1ab9e83443aed20e26bbf83a0e38

os_faults/api/node_collection.py

@@ -114,6 +114,14 @@ class NodeCollection(object):
             raise error.NodeCollectionError(msg)
         return self._make_instance(random.sample(self._hosts, count))
 
+    def filter(self, criteria_fn):
+        hosts = list(filter(criteria_fn, self._hosts))
+        if hosts:
+            return self._make_instance(hosts)
+        else:
+            raise error.NodeCollectionError(
+                'No nodes found according to criterion')
+
     def run_task(self, task, raise_on_error=True):
         """Run ansible task on node colection
 

os_faults/tests/unit/api/test_node_collection.py

@@ -155,6 +155,16 @@ class NodeCollectionTestCase(test.TestCase):
         self.assertEqual(1, len(one))
         self.assertIn(next(iter(one.hosts)), self.hosts)
 
+    def test_filter(self):
+        one = self.node_collection.filter(lambda host: host.ip == '10.0.0.2')
+        self.assertEqual(1, len(one))
+        self.assertEqual(self.hosts[0], one.hosts[0])
+
+    def test_filter_error(self):
+        self.assertRaises(error.NodeCollectionError,
+                          self.node_collection.filter,
+                          lambda host: host.ip == 'foo')
+
     def test_run_task(self):
         result = self.node_collection.run_task({'foo': 'bar'},
                                                raise_on_error=False)