Wait for disk when attaching volumes

It might take some time to discover new device in guest OS.
This patch adds waiter for device after we attached volume.

Change-Id: I1d35f6ed94fcd152a63f61ef6e073bc7fff40daa
Related-Prod: PROD-21942
(cherry picked from commit 4dc8f4e0e45a3798a3aa2cac37651acd014c4f28)
diff --git a/barbican_tempest_plugin/tests/scenario/test_volume_encryption.py b/barbican_tempest_plugin/tests/scenario/test_volume_encryption.py
index c7d2577..51491d4 100644
--- a/barbican_tempest_plugin/tests/scenario/test_volume_encryption.py
+++ b/barbican_tempest_plugin/tests/scenario/test_volume_encryption.py
@@ -16,7 +16,6 @@
 
 from oslo_log import log as logging
 from tempest.common import utils
-from tempest.common import waiters
 from tempest import config
 from tempest.lib import decorators
 from tempest.lib import exceptions as lib_exc
@@ -69,8 +68,7 @@
             if device_name in disks:
                 return
             if int(time.time()) - start >= wait_timeout:
-                message = ('Device %s did not appear in %d sec' % (
-                    device_name, wait_timeout))
+                message = 'Device %s was not found in %d sec' % wait_timeout
                 raise lib_exc.TimeoutException(message)
 
     def attach_detach_volume(self, server, volume, keypair):
@@ -79,13 +77,6 @@
 
         # Write a timestamp to volume
         server_ip = self.get_server_ip(server)
-        self.servers_client.stop_server(server['id'])
-        waiters.wait_for_server_status(self.servers_client, server['id'],
-                                       'SHUTOFF')
-
-        self.servers_client.start_server(server['id'])
-        waiters.wait_for_server_status(self.servers_client, server['id'],
-                                       'ACTIVE')
         self.wait_for_disk(server_ip, keypair,
                            CONF.compute.volume_device_name)
         timestamp = self.create_timestamp(