lagg: enable tests that stress the configuration changes

I wasn't able to reproduce a crash in several runs. Might be that
48698ead6ff0 or earlier changes have closed the races. In case crashes
with just enabled tests are registered, I will either work on them or
disable tests again.

lagg: propagate up/down to the children

Based on the old submission from asomers@. With modern state of locking
in lagg(4), the patch got much simplier. Enable the test that was
waiting for this change.

PR: 226144
Reviewed by: asomers
Differential Revision: https://reviews.freebsd.org/D44605

Remove $FreeBSD$: one-line sh pattern

Remove /^\s*#[#!]?\s*\$FreeBSD\$.*$\n/

Skip sys.net.if_lagg_test.status_stress in CI

This case panics the machine fairly often and we should run
stress tests separately.

Sponsored by: The FreeBSD Foundation

tests/sys/net/if_lagg_test: Fix syntax error

Fixes: ee231b27ff ("Also skip sys/net/if_lagg_test:witness on non-i386")

Also skip sys/net/if_lagg_test:witness on non-i386

The LOR also happens on amd64 and other architectures. Ideally we would
fix this. However, in order to get Jenkins green again to catch real
regressions, we should skip this test for now.

PR: 251726
Reviewed By: lwhsu
Differential Revision: https://reviews.freebsd.org/D29341

Skip sys.net.if_lagg_test.lacp_linkstate_destroy_stress in CI because of panic

PR: 244168
Sponsored by: The FreeBSD Foundation

Temporarily skip sys.net.if_lagg_test.lacp_linkstate_destroy_stress on i386 CI

It panics kernel

PR: 244168
Sponsored by: The FreeBSD Foundation

Temporarily skip failing sys.net.if_lagg_test.witness on i386 CI

PR: 244163
Sponsored by: The FreeBSD Foundation

Remove trailing whitespace

Sponsored by: The FreeBSD Foundation

Add tests for lagg(4) and other cloned network interfaces

Unfortunately, most of the tests are disabled because they fairly frequently
trigger panics.

MFC after: 3 weeks
Sponsored by: Spectra Logic Corp