Make GUI tests wait for 15 seconds
Make GUI tests wait for 15 seconds

The Gerrit page is basically rendered in the browser, and therefore
tests might randomly fail because the page is not fully rendered and
elements are not yet available.

This patch adds a grace time of 15 seconds before failing due to an
element that has not been found.

http://selenium-python.readthedocs.io/waits.html#implicit-waits

Change-Id: I6822ae8848b6daabbb7f71e48eeacc34dc056961

enovance/software-factory,enovance/software-factory,enovance/software-factory,enovance/software-factory,enovance/software-factory