Make sure devstack aborts if DIB fails

There are cases where DIB can fail to create an image but devstack
does not abort. This leads the gate job to run all the way down to
starting the tempest test before the job will fail out.
This adds a simple check for the image file and will abort early
if the image is not present.

Change-Id: I7ebf4137feb04827490dffc0dac3d6e4c8888075

devstack/plugin.sh

@@ -1,5 +1,8 @@
 #!/usr/bin/env bash
 
+saveenv=$-
+set -e
+
 # devstack plugin for octavia
 
 GET_PIP_CACHE_LOCATION=/opt/stack/cache/files/get-pip.py
@@ -110,6 +113,12 @@ function build_octavia_worker_image {
         sudo chown $STACK_USER ${dib_logs}
         $OCTAVIA_DIR/diskimage-create/diskimage-create.sh -l ${dib_logs}/$(basename $OCTAVIA_AMP_IMAGE_FILE).log $octavia_dib_tracing_arg -o $OCTAVIA_AMP_IMAGE_FILE ${PARAM_OCTAVIA_AMP_BASE_OS:-} ${PARAM_OCTAVIA_AMP_DISTRIBUTION_RELEASE_ID:-} ${PARAM_OCTAVIA_AMP_IMAGE_SIZE:-}
     fi
+
+    if ! [ -f $OCTAVIA_AMP_IMAGE_FILE ]; then
+        echo "Diskimage-builder failed to create the amphora image. Aborting."
+        exit 1
+    fi
+
     upload_image file://${OCTAVIA_AMP_IMAGE_FILE} $TOKEN
 
 }
@@ -799,3 +808,9 @@ if [[ "$1" == "clean" ]]; then
         octavia_cleanup
     fi
 fi
+
+if [[ $saveenv =~ e ]]; then
+    set -e
+else
+    set +e
+fi