Description of problem:
While running the selenium tests, test_labcontroller in IntegrationTests/src/bkr/inttest/server/selenium/test_distro_trees.py fails randomly with the following errors:

ERROR: test_labcontroller (bkr.inttest.server.selenium.test_distro_trees.DistroTreeViewTest)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/root/devel/beaker/IntegrationTests/src/bkr/inttest/server/selenium/test_distro_trees.py", line 60, in test_labcontroller
    b.find_element_by_xpath('//div[@class="flash"]').text,
  File "/usr/lib64/python2.6/site-packages/selenium/webdriver/remote/webdriver.py", line 214, in find_element_by_xpath
    return self.find_element(by=By.XPATH, value=xpath)
  File "/usr/lib64/python2.6/site-packages/selenium/webdriver/remote/webdriver.py", line 672, in find_element
    {'using': by, 'value': value})['value']
  File "/usr/lib64/python2.6/site-packages/selenium/webdriver/remote/webdriver.py", line 157, in execute
    self.error_handler.check_response(response)
  File "/usr/lib64/python2.6/site-packages/selenium/webdriver/remote/errorhandler.py", line 149, in check_response
    raise exception_class(message, screen, stacktrace)
NoSuchElementException: Message: u'Unable to locate element: {"method":"xpath","selector":"//div[@class=\\"flash\\"]"}' 


check the webdriver log, we can see:

webdriver [130226 15:46:21.57] [ 97.088s] [webdriver] Received command: clickElement
webdriver [130226 15:46:21.57] [ 97.093s] [webdriver] Using native events for click
webdriver [130226 15:46:21.58] [ 97.102s] [webdriver] Browser-specific offset (X,Y): 0, 89
webdriver [130226 15:46:22.40] [ 97.922s] [webdriver] Pending native events: false

compare to the success case, "Pending native events" should be "true" rather than "false" just after the clickElement command is received.  

This indicates the click event has been ignored by selenium/firefox, and there is a related issues in selenium group:
http://code.google.com/p/selenium/issues/detail?id=2864

we can simply workaround this by disable native events.

Version-Release number of selected component (if applicable):
selenium-server-standalone-2.21.0.jar
firefox-10.0.5-1.el6_2.x86_64

How reproducible:
about 10%

Steps to Reproduce:
1. ./run-tests.sh -sv bkr.inttest.server.selenium.test_distro_trees
2. repeat step 1 until see the failure
  
Actual results:
test_labcontroller failed

Expected results:


Additional info: