all.sh: Return error on keep-going failure

When calling all.sh from a script and using "--keep-going", errors were
sometimes missed due to all.sh always returning 0 "success" return code.
Return 1 if there is any failure encountered during a "keep-going" run.
diff --git a/tests/scripts/all.sh b/tests/scripts/all.sh
index 5c1ae2d..7868144 100755
--- a/tests/scripts/all.sh
+++ b/tests/scripts/all.sh
@@ -308,6 +308,7 @@
             echo "!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!"
             echo "${start_red}FAILED: $failure_count${end_color}$failure_summary"
             echo "!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!"
+            exit 1
         elif [ -z "${1-}" ]; then
             echo "SUCCESS :)"
         fi