Add missing removal of network interfaces in regress cleanup targets.
Reducing the risk tests conflicting with each other.

ok bluhm@

Use setup and cleanup feature from regress framework.
Remove echo headlines. Use consistent target names.
Makefile cleanup.

Before running the tests, consistently check whether interfaces or
routing domains are busy.

typos

Makefile cleanup, avoid DNS lookups, add copyright.

Move the test implementation into the Makefile. Then we have only
one place to look at. Make prints the commands it executes to
assist debugging and analysis. If the test fails, there are simple
r

Move the test implementation into the Makefile. Then we have only
one place to look at. Make prints the commands it executes to
assist debugging and analysis. If the test fails, there are simple
regress targets that can be run to reproduce the error easily.

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Move check for sysctl settings from shell script to makefile to
handle skipping consistently like other tests.

Add simple regress test for vxlan(4) and etherip(4).

ok bluhm