CLOUDSTACK-2071 - VirtualMachineManagerImpl.java start() method for instance

can fail to start a VM without notifying caller, if no exception is triggered.
The result is that VM start looks successful but was not. This fixes it by
throwing an exception at the very end if the object to be passed back is still
null.

Signed-off-by: Marcus Sorensen <marcus@betterservers.com> 1366225829 -0600

server/src/com/cloud/vm/VirtualMachineManagerImpl.java

@@ -866,6 +866,11 @@ public class VirtualMachineManagerImpl extends ManagerBase implements VirtualMac
             }
         }
 
+        if (startedVm == null) {
+            throw new CloudRuntimeException("Unable to start instance '" + vm.getHostName()
+                            + "' (" + vm.getUuid() + "), see management server log for details");
+        }
+
         return startedVm;
     }