Docker Studio - clean ContainerLinks of deleted containers

[mdutoo]

else NPE in synchronize() when stopping containers:

index 0dca939..bc588b1 100644
--- a/clouddesigner/org.occiware.clouddesigner.occi.docker.connector/src/org/occiware/clouddesigner/occi/docker/connector/DockerConnector.xtend
+++ b/clouddesigner/org.occiware.clouddesigner.occi.docker.connector/src/org/occiware/clouddesigner/occi/docker/connector/DockerConnector.xtend
@@ -1725,7 +1725,8 @@ abstract class MachineManager extends ComputeStateMachine {
if (compute.links.size > 0) {

                            // Stop the containers 

•                           compute.links.forEach[elt|(elt.target as ExecutableContainer).stop(StopMethod.GRACEFUL)]
  

•                           compute.links.filter[elt|elt.target != null] // else NPE
  

•                                   .forEach[elt|(elt.target as ExecutableContainer).stop(StopMethod.GRACEFUL)]
  
                    }
            }
  

[cgourdin]

null checks are done in docker studio v2.