Wait for SSHABLE in volume tests

Continuing the wait_until_sshable_pingable saga, add
wait_until='SSHABLE' to two more volume tests.

Change-Id: Idfbcdb3c1d2b9950f6f8dd59687c814cd3dcb660
diff --git a/tempest/api/volume/test_volumes_snapshots.py b/tempest/api/volume/test_volumes_snapshots.py
index a58da7e..b3a04f8 100644
--- a/tempest/api/volume/test_volumes_snapshots.py
+++ b/tempest/api/volume/test_volumes_snapshots.py
@@ -45,7 +45,7 @@
     def test_snapshot_create_delete_with_volume_in_use(self):
         """Test create/delete snapshot from volume attached to server"""
         # Create a test instance
-        server = self.create_server()
+        server = self.create_server(wait_until='SSHABLE')
         # NOTE(zhufl) Here we create volume from self.image_ref for adding
         # coverage for "creating snapshot from non-blank volume".
         volume = self.create_volume(imageRef=self.image_ref)
@@ -80,7 +80,7 @@
         snapshot1 = self.create_snapshot(self.volume_origin['id'])
 
         # Create a server and attach it
-        server = self.create_server()
+        server = self.create_server(wait_until='SSHABLE')
         self.attach_volume(server['id'], self.volume_origin['id'])
 
         # Now that the volume is attached, create other snapshots