update coverage timeout && add coverage exit code

Former-commit-id: 0c623d2348e73dc0c1df24f96098c4c5568e73ba

ci/jenkins/jenkinsfile/coverage.groovy

-timeout(time: 60, unit: 'MINUTES') {
+timeout(time: 30, unit: 'MINUTES') {
     dir ("ci/jenkins/scripts") {
         sh "./coverage.sh -o /opt/milvus -u root -p 123456 -t \$POD_IP"
         // Set some env variables so codecov detection script works correctly

ci/jenkins/scripts/coverage.sh

@@ -109,6 +109,7 @@ for test in `ls ${DIR_UNITTEST}`; do
     if [ $? -ne 0 ]; then
         echo ${args}
         echo ${DIR_UNITTEST}/${test} "run failed"
+        exit -1
     fi
 done
 
@@ -134,5 +135,10 @@ ${LCOV_CMD} -r "${FILE_INFO_OUTPUT}" -o "${FILE_INFO_OUTPUT_NEW}" \
     "*/src/utils/easylogging++.h" \
     "*/src/utils/easylogging++.cc"
 
+if [ $? -ne 0 ]; then
+    echo "gen ${FILE_INFO_OUTPUT_NEW} failed"
+    exit -2
+fi
+
 # gen html report
 # ${LCOV_GEN_CMD} "${FILE_INFO_OUTPUT_NEW}" --output-directory ${DIR_LCOV_OUTPUT}/