Experimental asset sync does not honor asset_roles during sync

[ess]

With the experimental_asset_sync feature enabled for a given app, the precompile_assets phase has two modes of operation: compiling assets and reusing assets.

Things work as expected when the deploy follows the "reuse" branch, but not when the deploy follows the "compile" branch.

Expected Behavior

Whether assets are reused or compiled, each instance that matches the asset_roles configured for the application will receive direction to either sync the new assets or reuse the previous build's assets, but no other instances receive any direction.

Actual Behavior

When assets are reused, each instance that matches the asset_roles configured for the application are directed to reuse the previous build's assets.

However, when assets are compiled, each instance that is not app_master is directed to sync the assets from app_master, including those not matching the configured asset_roles.

Affected Versions

Presumably all, but definitely 2.6.17 and 2.6.19, the two most recent published releases.

Aside

This bug was discovered by a single customer that relies on the incorrect behavior. They have added the proper asset_roles configuration to ensure that their desired behavior continues if this bug should be squashed.