Use common create_keypair method for autoscaling

The scenario test for autoscaling was implemented at the same time
with cleanup patch of create_keypair methods, and the cleanup patch
could not cover autoscaling test.
This patch covers autoscaling test.

Change-Id: Ibf4e98a9d4616c1dc6d2f08bde3d04a40b910067
diff --git a/tempest/scenario/manager.py b/tempest/scenario/manager.py
index 8290021..1cef612 100644
--- a/tempest/scenario/manager.py
+++ b/tempest/scenario/manager.py
@@ -589,7 +589,3 @@
     @classmethod
     def _stack_rand_name(cls):
         return rand_name(cls.__name__ + '-')
-
-    def _create_keypair(self):
-        kp_name = rand_name('keypair-smoke')
-        return self.compute_client.keypairs.create(kp_name)
diff --git a/tempest/scenario/orchestration/test_autoscaling.py b/tempest/scenario/orchestration/test_autoscaling.py
index cd959a8..17870a1 100644
--- a/tempest/scenario/orchestration/test_autoscaling.py
+++ b/tempest/scenario/orchestration/test_autoscaling.py
@@ -35,9 +35,8 @@
         if self.config.orchestration.keypair_name:
             self.keypair_name = self.config.orchestration.keypair_name
         else:
-            self.keypair = self._create_keypair()
+            self.keypair = self.create_keypair()
             self.keypair_name = self.keypair.id
-            self.set_resource('keypair', self.keypair)
 
     def launch_stack(self):
         self.parameters = {