Update attach logic in VolumeEncryptionTest

Pick the same logic as volume attach tests have, when after
volume attach server is rebooted to make sure guest OS
recognize new device.

Change-Id: I92098c7d994dc7d85643da29380866a805f4e869
Related-Prod: PRODX-5292
(cherry picked from commit 40bbd545a59328363c9ca8785d0d1eaed1eb8aed)
(cherry picked from commit c17ff148134712b8c8606608ef7d7abc789605ce)
(cherry picked from commit ff5888b9c37ff032f8314f1cbe2c121c48451eb5)
(cherry picked from commit f114587a68193407cbff7ebdc02bc6ce62204bf8)
(cherry picked from commit ac0a4a0d4d6c515f9739dd9f2ab35b235a3715d1)
diff --git a/barbican_tempest_plugin/tests/scenario/test_volume_encryption.py b/barbican_tempest_plugin/tests/scenario/test_volume_encryption.py
index 7613fa7..9aff4a4 100644
--- a/barbican_tempest_plugin/tests/scenario/test_volume_encryption.py
+++ b/barbican_tempest_plugin/tests/scenario/test_volume_encryption.py
@@ -13,13 +13,16 @@
 # under the License.
 
 import testtools
+import time
 
 from oslo_log import log as logging
 
 from tempest.common import utils
+from tempest.common import waiters
 from tempest import config
 from tempest.lib.common import api_version_utils
 from tempest.lib import decorators
+from tempest.lib import exceptions as lib_exc
 
 from barbican_tempest_plugin.tests.scenario import barbican_manager
 
@@ -72,12 +75,36 @@
                                     control_location='front-end')
         return self.create_volume(volume_type=volume_type['name'])
 
+    def wait_for_disk(self, server_ip, keypair, device_name, wait_interval=1,
+                      wait_timeout=15):
+        start = int(time.time())
+        ssh_client = self.get_remote_client(
+            server_ip, private_key=keypair['private_key'])
+        disks = ssh_client.get_disks()
+        while True:
+            time.sleep(wait_interval)
+            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))
+                raise lib_exc.TimeoutException(message)
+
     def attach_detach_volume(self, server, volume, keypair):
         # Attach volume
         self.nova_volume_attach(server, volume)
 
         # 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(
             server_ip,
             dev_name=CONF.compute.volume_device_name,