[Chain Task] end_func call msu_chain_task_delete

When the chian is finished and the end_func is called,
now, the chain task is also deleted.

Update code where chain_task_delete where called.

Signed-off-by: Ludovic Ferrandis <ludovic.ferrandis@intel.com>
[Chain Task] Better GUPnPServiceProxy management

Add weak pointer on GUPnPServiceProxy GObject

Remove msu_device_context_t  pointer from Chain Task parameters
and internal data. Use GUPnPServiceProxy pointer instead.

Add/Remove weak pointer for each proxy in each Chain Task

Remove weak pointer when an async task is finished or canceled.

Signed-off-by: Ludovic Ferrandis <ludovic.ferrandis@intel.com>