Use default image for test_encrypted_cinder_volumes

Use image specified in config as in case of image signature verification enabled
the newly created image will not work.

Related-Prod: PRODX-25629
Change-Id: I53162a706068cf9213d3d143fcfc61887430290d
diff --git a/tempest/scenario/test_encrypted_cinder_volumes.py b/tempest/scenario/test_encrypted_cinder_volumes.py
index df1af1f..5c59f1a 100644
--- a/tempest/scenario/test_encrypted_cinder_volumes.py
+++ b/tempest/scenario/test_encrypted_cinder_volumes.py
@@ -44,10 +44,9 @@
             raise cls.skipException('Encrypted volume attach is not supported')
 
     def launch_instance(self):
-        image = self.image_create()
         keypair = self.create_keypair()
 
-        return self.create_server(image_id=image, key_name=keypair['name'])
+        return self.create_server(key_name=keypair['name'])
 
     def attach_detach_volume(self, server, volume):
         attached_volume = self.nova_volume_attach(server, volume)