Re-futurizing this future, but skipping it for segment 'fast'
This is a clone of remoteString3, tested only for segment 'fast'

When the original future passes, this test should be removed,
along with the .skipif on the original.
Merge pull request #620 from bradcray/remoteString3-future-edits

Edits to David's remoteString3 test

[reviewed by @daviditen]

David's remoteString3 future recently started passing for gasnet-fast
testing, so Sung unfuturized it. However, it still seems to fail for
gasnet-everything. For that reason, I'm refuturizing it, but with a
skipif to avoid false positives in the gasnet-fast case. Simultaneously,
I've added a clone of the test to lock in the gasnet-fast behavior since
it's working there for the time being. I have a question out to Sung
wondering what would cause the difference.

When remoteString3.future is retired, its skipif should be removed,
as should the new remoteString3-seg-fast.chpl test.