skipped callback in loop does not display 'item'.

I noticed that when a module returns 'skipped':True while using a with_items loop, the skipped callback does not display the current item label like ok or changed does.

Investigating the code in runner/__init__.py, it seems that the item is not being passed through on line 887, but is on line 714. Note: There is another call to on_skipped on line 673, but that seems like it should never have 'item' set.

This patch brings consistency and fixes the issue for me. 

*Before*
```
TASK: [Skipping Test ] *********************************************** 
skipping: [192.168.66.10]
skipping: [192.168.66.10]
skipping: [192.168.66.10]
```

*After*
```
TASK: [Skipping Test ] *********************************************** 
skipping: [192.168.66.10] => (item=redis)
skipping: [192.168.66.10] => (item=varnish)
skipping: [192.168.66.10] => (item=nginx)
```