Bees: fix async_lwt worker initialization

What

Do not create domains too early.

Why

When running a node, some Unix.fork occurs after we have trigger on_main_run, leading to an error because we started a domain for the async lwt loop.

How

Do not run in a separate domain

Manually testing the MR

Checklist

• Document the interface of any function added or modified (see the coding guidelines)
• Document any change to the user interface, including configuration parameters (see node configuration)
• Provide automatic testing (see the testing guide).
• For new features and bug fixes, add an item in the appropriate changelog (docs/protocols/alpha.rst for the protocol and the environment, CHANGES.rst at the root of the repository for everything else).
• Select suitable reviewers using the Reviewers field below.
• Select as Assignee the next person who should take action on that MR