Fix NullPointerException after restart of Jenkins controller when age…

…nt resumes from suspend (#187)

* Made field non transient and make sure it is not null

* Made the map transient again to avoid serialization

Co-authored-by: Rudolph, Nils <[email protected]>

src/main/java/com/microsoft/azure/vmagent/AzureVMCloud.java

@@ -132,7 +132,7 @@ public class AzureVMCloud extends Cloud {
     private List<AzureTagPair> cloudTags;
 
     //The map should not be accessed without acquiring a lock of the map
-    private final transient Map<AzureVMAgent, AtomicInteger> agentLocks = new HashMap<>();
+    private transient Map<AzureVMAgent, AtomicInteger> agentLocks = new HashMap<>();
 
     private Supplier<Azure> createAzureClientSupplier() {
         return Suppliers.memoize(() -> AzureClientUtil.getClient(credentialsId))::get;
@@ -202,6 +202,10 @@ private Object readResolve() {
                 instTemplates = null;
             }
 
+            if (agentLocks == null) {
+                agentLocks = new HashMap<>();
+            }
+
             // Walk the list of templates and assign the parent cloud (which is transient).
             ensureVmTemplateList();
             for (AzureVMAgentTemplate template : vmTemplates) {