provider/aws: Fix source_dest_check with network_interface

[grubernaut]

The default value for source_dest_check needs to remain the same, so as not to break any backwards compatibility, however, adding a new network_interface parameter with a pre-configured network_interface that has source_dest_check set to false throws a diff after initial apply. Since we don't want to change source_dest_check to computed in order to not break sane defaults, ignore the diff thrown if network_interface attributes are configured on an instance.

$ make testacc TEST=./builtin/providers/aws TESTARGS="-run=TestAccAWSInstance_primaryNetworkInterfaceSourceDestCheck"
==> Checking that code complies with gofmt requirements...
go generate $(go list ./... | grep -v /terraform/vendor/)
2017/04/28 16:26:02 Generated command/internal_plugin_list.go
TF_ACC=1 go test ./builtin/providers/aws -v -run=TestAccAWSInstance_primaryNetworkInterfaceSourceDestCheck -timeout 120m
=== RUN   TestAccAWSInstance_primaryNetworkInterfaceSourceDestCheck
--- PASS: TestAccAWSInstance_primaryNetworkInterfaceSourceDestCheck (134.20s)
PASS
ok      github.com/hashicorp/terraform/builtin/providers/aws    134.211s

$ make testacc TEST=./builtin/providers/aws TESTARGS="-run=TestAccAWSInstance_sourceDestCheck"
==> Checking that code complies with gofmt requirements...
go generate $(go list ./... | grep -v /terraform/vendor/)
2017/04/28 16:15:14 Generated command/internal_plugin_list.go
TF_ACC=1 go test ./builtin/providers/aws -v -run=TestAccAWSInstance_sourceDestCheck -timeout 120m
=== RUN   TestAccAWSInstance_sourceDestCheck
--- PASS: TestAccAWSInstance_sourceDestCheck (179.81s)
PASS
ok      github.com/hashicorp/terraform/builtin/providers/aws   179.815s

Fixes: #14068

[catsby]

LGTM, thanks for showing the tests 👍

[ghost]

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