Revert "Bug 1017002 - [Homescreen] Disable intermittent Marionette JS failure on Travis: 1) Homescreen navigation > Going to the homescreen and back to a warm app: AssertionError: we got 2 reflows instead of 0"

This reverts commit e8a553c0c6c3657a536f4cd409173e1d561263b9.
Merge pull request #21741 from KevinGrandon/bug_1017002_check_reenabling_test_2

Revert "Bug 1017002 - [Homescreen] Disable intermittent Marionette JS failure on Travis: 1) Homescreen navigation > Going to the homescreen and back to a warm app: AssertionError: we got 2 reflows instead of 0"