NCBC-709: Make sure all Task/Task<T> call ConfigureAwait(false)

Change-Id: I259e702911bcdd56c7e2c341d2564be8bb1ccdac
Reviewed-on: http://review.couchbase.org/42647
Tested-by: Jeffry Morris <jeffrymorris@gmail.com>
Reviewed-by: Brett Lawson <brett19@gmail.com>