Update task status on ZK if acquire was successful to reset previous state (#990)

Author: akshayrai

datastream-server/src/main/java/com/linkedin/datastream/server/DatastreamTaskImpl.java

@@ -337,6 +337,7 @@ public void acquire(Duration timeout) {
       });
 
       _zkAdapter.acquireTask(this, timeout);
+      setStatus(DatastreamTaskStatus.ok("Task lock acquired"));
     } catch (Exception e) {
       LOG.error(String.format("Failed to acquire task: %s with dependencies: %s", this.getDatastreamTaskName(),
           String.join(",", this.getDependencies())), e);