Milo: Add step text for swarming task exceptions

appengine/cmd/milo/swarming/testdata/build-canceled.swarm

Index: appengine/cmd/milo/swarming/testdata/build-canceled.swarm
diff --git a/appengine/cmd/milo/swarming/testdata/build-timeout.swarm b/appengine/cmd/milo/swarming/testdata/build-canceled.swarm
similarity index 98%
copy from appengine/cmd/milo/swarming/testdata/build-timeout.swarm
copy to appengine/cmd/milo/swarming/testdata/build-canceled.swarm
index 369f8834053133bf9f4b9b9ca55a575ab8998798..938ba8176ebe16b4c967ea57181073fc4e9bf453 100644
--- a/appengine/cmd/milo/swarming/testdata/build-timeout.swarm
+++ b/appengine/cmd/milo/swarming/testdata/build-canceled.swarm
@@ -26,7 +26,7 @@
  ],
  "bot_dimensions": [
   {
-   "value": [
+  "value": [
     "8"
    ],
    "key": "cores"
@@ -85,7 +85,7 @@
  "exit_code": "-15",
  "name": "buildbucket-estaab-infra-waterfall-test-infra-continuous-precise-32",
  "failure": true,
- "state": "TIMED_OUT",
+ "state": "CANCELED",
  "modified_ts": "2016-03-14T11:00:18.486020",
  "user": "",
  "bot_id": "swarm3-c4",