allow env override of thread count #2373

Author: ptrthomas

karate-core/src/main/java/com/intuit/karate/Runner.java

@@ -95,7 +95,7 @@ public static class Builder<T extends Builder> {
         File workingDir;
         String buildDir;
         String configDir;
-        int threadCount;
+        int threadCount = 1;
         int timeoutMinutes;
         String reportDir;
         String scenarioName;
@@ -181,6 +181,9 @@ public List<FeatureCall> resolveAll() {
                 if (ko.paths != null) {
                     paths = ko.paths;
                 }
+                if (ko.threads != threadCount) { // 1 by default
+                    threadCount = ko.threads;
+                }
                 dryRun = ko.dryRun || dryRun;
             }
             String tempEnv = StringUtils.trimToNull(systemProperties.get(Constants.KARATE_ENV));