Fix dropdown menu does not open with firefox 34

Firefox update changed behaviour of the selenium tests, it is not
enough to click on the div representing dropdown menu region,
one must click on the first child (which is now button, but i suppose
it can change over time to input or anything else) in order to open the
dropdown menu.

Closes-Bug: #1399268
Partially implements blueprint: selenium-integration-testing

Change-Id: If9aed4b547f843d16ba729f84cb2c02acb2a0a4d
Merge "Fix dropdown menu does not open with firefox 34"