All this commit does is add a call to `normalizeJsonString`, so the
settings returned by the AWS API and the settings set by users in the tf
config don't indicate diffs in the tf state whenever there's extra
whitespace in the JSON. I added a case to the `structure_test.go` file, to
verify that `normalizeJsonString` treats regular strings the way I'd
expect.

I would have added an acceptance test, but the 15-20 minute feedback loop
is far too long to be practical. I tried figuring out a way to spoof the
flow instead, but had no luck.