Record provider AZ info in graphite.

When constructing launchStats() subkeys for graphite send the existing
key data but also add a key for provider.az info if we have an az.
This rolls up the az data into non az prefixed key but also provides az
specific information. This will track launch stats for individual AZs.

Change-Id: Ie67238950e9bd927f942f21fadb7f3e894de118d
Merge "Record provider AZ info in graphite."