fix provisionCertificate api returns NPE when 'reconnect' parameter is true (apache#2756)

This PR fixes NPE with the provisionCertificateCmd when reconnect is set to True.

Also fixes the following Marvin test failures:
- test_certauthority_root.py

Author: Dingane Hlaluku

engine/orchestration/src/main/java/com/cloud/agent/manager/ClusteredAgentManagerImpl.java

@@ -367,10 +367,10 @@ public void reconnect(final long hostId) throws CloudRuntimeException, AgentUnav
         Boolean result = propagateAgentEvent(hostId, Event.ShutdownRequested);
         if (result == null) {
             super.reconnect(hostId);
-
+            return;
         }
         if (!result) {
-            throw new CloudRuntimeException("Failed to propagating agent change request event:" + Event.ShutdownRequested + " to host:" + hostId);
+                throw new CloudRuntimeException("Failed to propagate agent change request event:" + Event.ShutdownRequested + " to host:" + hostId);
         }
     }