Test script should return exit code from test run

And the script should not crash if no error screenshot is generated.

Bug: 129345960
Test: run test script
Change-Id: Ifb6c4539387ad956d5d31bbc4820f612b7cd1ce0
(cherry picked from commit 1e345655bb99409c678df9328b92243d9a80d330)
1 file changed