Modify HostingSubscription_requestRootSoftwareInstance in order to avoid starting/stopping a destroyed computer partition.

Modify HostingSubscription_requestRootSoftwareInstance in order to pass testVifibSlapBang.test_computer_bang_not_called_on_partly_destroyed_tree

It is not allowed to access to collections.deque in a python script.
Let switch back to poor man queue using python native lists.

This reverts commit 18060ee5.

Conflicts:

	master/bt5/vifib_base/bt/revision

Check connection from root hosting subscription instead of root software instance in SoftwareInstance_requestSoftwareInstance

Add root_software_release_url property on Hosting Subscription in order to store the requested software_release.

Add root_state_property on Hosting Subscription in order to store to which state the root instance was requested.

This reverts commit 99d1c52c.

My mistake. We used :
  dict.get("key") or "default"
instead of :
  dict.get("key", "default")

because some time dict["key"] is None.

This avoid looping on one item.

- Use Hosting Subscribtion as root
- Rename 'SoftwareInstance_getSoftwareInstanceUid' into
  'SoftwareInstance_getHostingSubscriptionUid' to have a meanful name.

string to vifib master.