[mock_cobalt] check errors and avoid spawn_local
...preferring returning futures explicitly so that they can be
scheduled by application code in main and in tests.
Test:
fx run-test netstack_integration_tests -t \
netstack_cobalt_integration_test
Change-Id: I5f287efe618406579f80ded4387ec7a899671ad8
Pink + Purple == Fuchsia (a new operating system)
Fuchsia is a modular, capability-based operating system. Fuchsia runs on modern 64-bit Intel and ARM processors.
Fuchsia is an open source project with a code of conduct that we expect everyone who interacts with the project to respect.
See Getting Started.
See fuchsia.dev.