Updated unlock screen fails often

[Francis Ginther]

The updated unlock_screen script continues to fail frequently. This may actually be caused by a unity8 crash (all the builds I've examined with this issue have one).

Adding some retries could work around the issue and allow us to get more reliable tests.

[console log]
[from http://10.97.0.26:8080/job/generic-mediumtests-runner-mako/2598/consoleText]
I: Turning on the display
I: Unlocking screen
phablet 1919 1742 7 17:42 ? 00:00:05 unity8
root 4102 570 0 17:43 pts/13 00:00:00 /bin/bash -c ps -ef|grep unity8
root 4105 4102 0 17:43 pts/13 00:00:00 grep unity8
----------------------------------------------------------------------
Stopping Unity
unity8 stop/waiting
Unity stopped
----------------------------------------------------------------------
Taking screen lock (#1235000)
----------------------------------------------------------------------
Starting Unity with testability
unity8 start/running, process 4156
Unity started
----------------------------------------------------------------------
Releasing screen lock (#1235000)
----------------------------------------------------------------------
Cleaned up upstart override
----------------------------------------------------------------------
Turning on the screen

----------------------------------------------------------------------
Executing Swipe
Traceback (most recent call last):
  File "/home/phablet/autopilot-testrunner/unlock_screen.py", line 106, in <module>
    unlock_screen()
  File "/home/phablet/autopilot-testrunner/unlock_screen.py", line 60, in unlock_screen
    unity8 = introspection.get_proxy_object_for_existing_process(connection_name=conn)
  File "/usr/lib/python2.7/dist-packages/autopilot/introspection/__init__.py", line 271, in get_proxy_object_for_existing_process
    raise ProcessSearchError("Search criteria returned no results")
autopilot.introspection.ProcessSearchError: Search criteria returned no results
Loading tests from: /usr/lib/python2.7/dist-packages

[Francis Ginther (fginther)]

The test runner was updated to retry the unlock up to 5 times. This is really a workaround for the unlock failure itself, but app tests are much more useful now.

[Cris Dywan (kalikiana)]

I still get "E: Unlock failed, no more retries" here https://code.launchpad.net/~kalikiana/ubuntu-ui-toolkit/checktrigger/+merge/188547 (https://jenkins.qa.ubuntu.com/job/generic-mediumtests-runner-mako/2746/console).