Do static template validation for nested stacks

Currently we don't fail fast, even if there is an error
in the nested template which should fail validation.
This change to recurse and do static template validation
for nested stack resources.

Change-Id: I572ded640582419e0888e4b9f8eed3a3432d6121
Closes-Bug: #1388140
Closes-Bug: #1389104
Merge "Do static template validation for nested stacks"