ci: fix test/test-testsuite targets output parsing

Prevent tparse from breaking by filtering non-JSON lines (it works! and
has no drawbacks, I think?).

Change-Id: I8b17d7c240e77950d800fd3c1f16e15ef60f79d6

Author: amwolff

Jenkinsfile

@@ -88,7 +88,7 @@ pipeline {
                                 STORJ_TEST_LOG_LEVEL = 'info'
                             }
                             steps {
-                                sh 'make test 2>&1 | tee .build/tests.json | xunit -out .build/tests.xml'
+                                sh 'make test 2>&1 | grep "^{.*" | tee .build/tests.json | xunit -out .build/tests.xml'
                             }
                             post {
                                 always {
@@ -115,7 +115,7 @@ pipeline {
                             }
                             post {
                                 always {
-                                    sh script: 'cat .build/testsuite.json | tparse -all -top -slow 100', returnStatus: true
+                                    sh script: 'cat .build/testsuite.json | grep "^{.*" | tparse -all -top -slow 100', returnStatus: true
                                     archiveArtifacts artifacts: '.build/testsuite.json'
                                     junit '.build/testsuite.xml'
                                 }