Bug 1086277 - Add a test for add & delete a divider on homescreen

You're right, it's just renaming an existing 1-line-method. But, if somebody new to the homescreen doesn't know that pressing the home button exit the edit mode, this person might not understand the steps of the test. That's the value I see in putting this line in the Page class.

Moreover, if one day, the home button is used for something else on the homescreen, we would need to replace just one line in the Page class, instead of many lines in each test.