Remove devstack exercises

These seem to be not run for quite some time and they don't
succeed anymore - drop the code to avoid somebody accidentally
running it and wondering. A good example of "if it isn't tested
its broken".

Depends-On: https://review.openstack.org/583146
Depends-On: https://review.openstack.org/583147

Change-Id: I99e8a5ca2925217a5a2401984f3f4f6f032017be
diff --git a/doc/source/configuration.rst b/doc/source/configuration.rst
index 7efe4d6..46e50df 100644
--- a/doc/source/configuration.rst
+++ b/doc/source/configuration.rst
@@ -665,8 +665,7 @@
     enable_service n-cell
 
 Be aware that there are some features currently missing in cells, one
-notable one being security groups.  The exercises have been patched to
-disable functionality not supported by cells.
+notable one being security groups.
 
 Cinder
 ~~~~~~
@@ -729,44 +728,6 @@
 
     ENABLE_IDENTITY_V2=False
 
-Exercises
-~~~~~~~~~
-
-``exerciserc`` is used to configure settings for the exercise scripts.
-The values shown below are the default values. These can all be
-overridden by setting them in the ``localrc`` section.
-
-* Max time to wait while vm goes from build to active state
-
-    ::
-
-        ACTIVE_TIMEOUT==30
-
-* Max time to wait for proper IP association and dis-association.
-
-    ::
-
-        ASSOCIATE_TIMEOUT=15
-
-* Max time till the vm is bootable
-
-    ::
-
-        BOOT_TIMEOUT=30
-
-* Max time from run instance command until it is running
-
-    ::
-
-        RUNNING_TIMEOUT=$(($BOOT_TIMEOUT + $ACTIVE_TIMEOUT))
-
-* Max time to wait for a vm to terminate
-
-    ::
-
-        TERMINATE_TIMEOUT=30
-
-
 .. _arch-configuration:
 
 Architectures