SAMZA-2798: Populate worker.opts in environment variable only if available (#1693)

Description
Populate worker.opts in the environment variable only if available in the configs.

Changes
Check if worker.opts is present and then add it to environment variable

Tests
Updated unit tests

Author: mynameborat

samza-core/src/main/java/org/apache/samza/job/ShellCommandBuilder.java

@@ -44,9 +44,10 @@ public Map<String, String> buildEnvironment() {
     envBuilder.put(ShellCommandConfig.ENV_CONTAINER_ID, this.id);
     envBuilder.put(ShellCommandConfig.ENV_COORDINATOR_URL, this.url.toString());
     envBuilder.put(ShellCommandConfig.ENV_JAVA_OPTS, shellCommandConfig.getTaskOpts().orElse(""));
-    envBuilder.put(ShellCommandConfig.WORKER_JVM_OPTS, shellCommandConfig.getWorkerOpts().orElse(""));
     envBuilder.put(ShellCommandConfig.ENV_ADDITIONAL_CLASSPATH_DIR,
         shellCommandConfig.getAdditionalClasspathDir().orElse(""));
+    shellCommandConfig.getWorkerOpts()
+        .ifPresent(workerOpts -> envBuilder.put(ShellCommandConfig.WORKER_JVM_OPTS, workerOpts));
     shellCommandConfig.getJavaHome().ifPresent(javaHome -> envBuilder.put(ShellCommandConfig.ENV_JAVA_HOME, javaHome));
     return envBuilder.build();
   }

samza-core/src/test/java/org/apache/samza/job/TestShellCommandBuilder.java

@@ -45,7 +45,6 @@ public void testBasicBuild() throws MalformedURLException {
         ShellCommandConfig.ENV_CONTAINER_ID, "1",
         ShellCommandConfig.ENV_COORDINATOR_URL, URL_STRING,
         ShellCommandConfig.ENV_JAVA_OPTS, "",
-        ShellCommandConfig.WORKER_JVM_OPTS, "",
         ShellCommandConfig.ENV_ADDITIONAL_CLASSPATH_DIR, "");
     // assertions when command path is not set
     assertEquals("foo", shellCommandBuilder.buildCommand());