Correct misspelt word in msg in test_images.py

msg = ("The container format and the disk format don't match. "
       "Contaiter format: %(container)s, Disk format: %(disk)s." %
       {'container': container_format, 'disk': disk_format})

    "Contaiter" should be "Container"

Change-Id: Ib8b3fae328fb004ee367b19ed41385b1d325fb46
Closes-Bug: #1580823
diff --git a/tempest/api/image/v1/test_images.py b/tempest/api/image/v1/test_images.py
index 1a84d06..cad22f3 100644
--- a/tempest/api/image/v1/test_images.py
+++ b/tempest/api/image/v1/test_images.py
@@ -32,7 +32,7 @@
 
     if container_format in a_formats and container_format != disk_format:
         msg = ("The container format and the disk format don't match. "
-               "Contaiter format: %(container)s, Disk format: %(disk)s." %
+               "Container format: %(container)s, Disk format: %(disk)s." %
                {'container': container_format, 'disk': disk_format})
         raise exceptions.InvalidConfiguration(message=msg)