Actually append jvm opts to the CLI

- Also adds a test

client/driver/java.go

@@ -138,6 +138,7 @@ func (d *JavaDriver) Start(ctx *ExecContext, task *structs.Task) (DriverHandle,
 	jvm_options, ok := task.Config["jvm_options"]
 	if ok && jvm_options != "" {
 		d.logger.Printf("[DEBUG] driver.java: found JVM options: %s", jvm_options)
+		args = append(args, jvm_options)
 	}
 
 	// Build the argument list

client/driver/java_test.go

@@ -100,6 +100,7 @@ func TestJavaDriver_Start_Wait(t *testing.T) {
 			"jar_source": "https://dl.dropboxusercontent.com/u/47675/jar_thing/demoapp.jar",
 			// "jar_source": "https://s3-us-west-2.amazonaws.com/java-jar-thing/demoapp.jar",
 			// "args": "-d64",
+			"jvm_options": "-Xmx2048m -Xms256m",
 		},
 		Resources: basicResources,
 	}