Merge changes from origin/7.1

5b2ddc1 Make test work reliably by activating @Push
10ca7ed Catch and log exceptions in session lifecycle listeners (#12915)
8abf434 Move working sass tests from sasslangbroken to sasslang.
1ac492e Move a sass test that no longer fails.

Change-Id: I960e80fd2120c20bc7b042eccbadb1e748ec0f00

diff --cc server/src/com/vaadin/server/VaadinService.java
Simple merge