Python3 common patterns

Modify some codes in order to make them meet
the Python3 common pattern.
In this patch,I replace filter(lambda obj: test(obj),data)
with[obj for obj in data if test(obj)]

Change-Id: I68e76f91dc31aa0e00124c1eb76a0a1f0178cc44

mistral_tempest_tests/services/base.py

@@ -41,7 +41,7 @@ def find_items(items, **props):
 
         return True
 
-    filtered = list(filter(lambda item: _matches(item, **props), items))
+    filtered = list([item for item in items if _matches(item, **props)])
 
     if len(filtered) == 1:
         return filtered[0]

mistral_tempest_tests/tests/scenario/engine/actions/v2/test_ssh_actions.py

@@ -79,7 +79,7 @@ class SSHActionsTestsV2(base.TestCaseAdvanced):
             'floating_ips'
         )
         free_ips = list(
-            filter(lambda fl_ip: fl_ip['instance_id'] is None, all_ips)
+            [fl_ip for fl_ip in all_ips if fl_ip['instance_id'] is None]
         )
 
         if free_ips: