Libcloud 544 gce metadata fix

This is a slightly improved version of the fix i submitted minutes ago which had some trace-generating code in it. Removed my own silly tests.
I've already staged the ValueError, that's good and i have it staged locally.

I do believe we can't do the aforementioned code as that would re-introduce the issue i'm attempting to fix.This is the output of that code that gets sent to GCE while running it:
```
{'items': [{'value': [{'value': '1', 'key': 'items'}, {'value': 'two', 'key': '2'}, {'value': 'testbox', 'key': 'salt-cloud-profile'}], 'key': 'items'}]}
```

This is what salt sends to libcloud:
```
{'items': [{'value': '1', 'key': 'items'}, {'value': 'two', 'key': '2'}, {'value': 'testbox', 'key': 'salt-cloud-profile'}]}
```

I'll have a closer, fresher look on Monday and find a better way to handle this. 

Cheers and have a great weekend!