Narrow assertion in attach/delete volume test

The attach_delete_volume test takes the device name
from tempest.conf's volume_device_name and looks for the output
in /proc/partition.  It could be that this name occurs in part of
another partition's string.  Patch adjusts the name used in the
assertion to make sure it's an exact match.

Change-Id: I570864c7c38969dcdcbfa5bd71be0348d90bd790
Closes-Bug: #1619564
diff --git a/tempest/api/compute/volumes/test_attach_volume.py b/tempest/api/compute/volumes/test_attach_volume.py
index a5c303c..9f05a84 100644
--- a/tempest/api/compute/volumes/test_attach_volume.py
+++ b/tempest/api/compute/volumes/test_attach_volume.py
@@ -135,7 +135,8 @@
                 servers_client=self.servers_client)
 
             partitions = linux_client.get_partitions()
-            self.assertIn(self.device, partitions)
+            device_name_to_match = ' ' + self.device + '\n'
+            self.assertIn(device_name_to_match, partitions)
 
         self._detach(self.server['id'], self.volume['id'])
         self.attachment = None
@@ -157,7 +158,7 @@
                 servers_client=self.servers_client)
 
             partitions = linux_client.get_partitions()
-            self.assertNotIn(self.device, partitions)
+            self.assertNotIn(device_name_to_match, partitions)
 
     @test.idempotent_id('7fa563fe-f0f7-43eb-9e22-a1ece036b513')
     def test_list_get_volume_attachments(self):