Remove support for 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".

Needed-By: https://review.openstack.org/#/c/581377/

Change-Id: I68d7099e6f5be502f8a578818b5e2e4c82889c15

devstack-vm-gate-wrap.sh

@@ -157,9 +157,6 @@ export DEVSTACK_GATE_TEMPEST=${DEVSTACK_GATE_TEMPEST:-0}
 # installed and configured, but the tests will be skipped
 export DEVSTACK_GATE_TEMPEST_NOTESTS=${DEVSTACK_GATE_TEMPEST_NOTESTS:-0}
 
-# Set to 1 to run the devstack exercises
-export DEVSTACK_GATE_EXERCISES=${DEVSTACK_GATE_EXERCISES:-0}
-
 # Set to 1 to run postgresql instead of mysql
 export DEVSTACK_GATE_POSTGRES=${DEVSTACK_GATE_POSTGRES:-0}
 

devstack-vm-gate.sh

@@ -813,12 +813,6 @@ if [[ "$DEVSTACK_GATE_REMOVE_STACK_SUDO" -eq 1 ]]; then
         -a "path=/etc/sudoers.d/50_stack_sh state=absent"
 fi
 
-if [[ "$DEVSTACK_GATE_EXERCISES" -eq "1" ]]; then
-    echo "Running devstack exercises"
-    $ANSIBLE all -f 5 -i "$WORKSPACE/inventory" -m shell \
-        -a "cd '$BASE/new/devstack' && sudo -H -u stack ./exercise.sh"
-fi
-
 if [[ "$DEVSTACK_GATE_TEMPEST" -eq "1" ]]; then
     # under tempest isolation tempest will need to write .tox dir, log files
     if [[ -d "$BASE/new/tempest" ]]; then