This extends the work in #11668 to enable final snapshots by default.
This time it's for redshift
```
% make testacc TEST=./builtin/providers/aws TESTARGS='-run=TestAccAWSRedshiftCluster_withFinalSnapshot'
==> Checking that code complies with gofmt requirements...
go generate $(go list ./... | grep -v /terraform/vendor/)
2017/02/04 13:53:02 Generated command/internal_plugin_list.go
TF_ACC=1 go test ./builtin/providers/aws -v -run=TestAccAWSRedshiftCluster_withFinalSnapshot -timeout 120m
=== RUN TestAccAWSRedshiftCluster_withFinalSnapshot
--- PASS: TestAccAWSRedshiftCluster_withFinalSnapshot (859.96s)
PASS
ok github.com/hashicorp/terraform/builtin/providers/aws 859.986s
```
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