Make triton machine deletes synchronous.

[sean-]

It is required for DELETE operations to return a non-nil response:

terraform/helper/resource/state.go

Line 126 in 4c3a053

if res == nil {

I desired, I can include a follow on commit to this PR that updates helper/resource/state.go's comment re: StateRefreshFunc/WaitForState() to note that DELETE-like operations should include a non-nil response. Something akin to:

diff --git a/helper/resource/state.go b/helper/resource/state.go
index 37c586a11..d1c99a963 100644
--- a/helper/resource/state.go
+++ b/helper/resource/state.go
@@ -13,7 +13,8 @@ var refreshGracePeriod = 30 * time.Second
 // It returns three results. `result` is any object that will be returned
 // as the final object after waiting for state change. This allows you to
 // return the final updated object, for example an EC2 instance after refreshing
-// it.
+// it.  The result object must be non-nil even if the case where the target
+// state has been achieved (e.g. DELETE operations).
 //
 // `state` is the latest state of that object. And `err` is any error that
 // may have happened while refreshing the state.

[ghost]

I'm going to lock this issue because it has been closed for 30 days ⏳. This helps our maintainers find and focus on the active issues.

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