tweak CSM config to be able to enabled by only environment or config

.changes/next-release/feature-client side monitoring-f83de457.json

@@ -0,0 +1,5 @@
+{
+  "type": "feature",
+  "category": "client side monitoring",
+  "description": "CSM now can be enabled globally only from environment without code change"
+}

lib/service.js

@@ -57,7 +57,7 @@ AWS.Service = inherit({
     //enable attaching listeners to service client
     AWS.SequentialExecutor.call(this);
     AWS.Service.addDefaultMonitoringListeners(this);
-    if (this.config.clientSideMonitoring && this.publisher) {
+    if ((this.config.clientSideMonitoring || AWS.Service._clientSideMonitoring) && this.publisher) {
       var publisher = this.publisher;
       this.addNamedListener('PUBLISH_API_CALL', 'apiCall', function PUBLISH_API_CALL(event) {
         process.nextTick(function() {publisher.eventHandler(event);});
@@ -709,7 +709,12 @@ AWS.util.update(AWS.Service, {
     if (!this.prototype.publisher && AWS.util.clientSideMonitoring) {
       var Publisher = AWS.util.clientSideMonitoring.Publisher;
       var configProvider = AWS.util.clientSideMonitoring.configProvider;
-      this.prototype.publisher = new Publisher(configProvider());
+      var publisherConfig = configProvider();
+      this.prototype.publisher = new Publisher(publisherConfig);
+      if (publisherConfig.enabled) {
+        //if csm is enabled in environment, SDK should send all metrics
+        AWS.Service._clientSideMonitoring = true;
+      }
     }
     AWS.SequentialExecutor.call(svc.prototype);
     AWS.Service.addDefaultMonitoringListeners(svc.prototype);

test/publisher/functional_test/runner.spec.js

@@ -14,7 +14,6 @@ describe('run functional test', () => {
   let defaultConfiguration;
   let processEnvBackup;
   before(() => {
-    AWS.config.clientSideMonitoring = true;
     processEnvBackup = Object.assign({}, process.env);
   });