fix parallel test exit scenario. introduced in 4d8b371908

.travis.yml

@@ -55,4 +55,4 @@ before_script:
 
 script:
     # run test suite directories in parallel using GNU parallel
-    - ls -d tests/Composer/Test/* | parallel --gnu --keep-order 'echo "Running {} tests"; ./vendor/bin/phpunit -c tests/complete.phpunit.xml --colors=always {} || (echo -e "\e[41mFAILED\e[0m {}" && $(exit 1));'
+    - ls -d tests/Composer/Test/* | parallel --gnu --keep-order 'echo "Running {} tests"; ./vendor/bin/phpunit -c tests/complete.phpunit.xml --colors=always {} || (echo -e "\e[41mFAILED\e[0m {}" && exit 1);'