Fix evaluation-order assumption in futures varidic collect
Fix evaluation-order assumption in futures varidic collect

Summary: [Folly] Fix evaluation-order assumption in futures varidic collect - argument evaluation order is unspecified so it must not be relied on when side-effects must occur in a specific order.

Reviewed By: lewissbaker

Differential Revision: D19347873

fbshipit-source-id: db4326d995a241619f96ff2bacdf5a5fa2332091

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