if_ovpn tests: destroy an if_ovpn interface before it's been used

[kp]

Summary

Ensure that we correctly clean up even if the interface never gets a socket
assigned.

Sponsored by: Rubicon Communications, LLC ("Netgate")

[markj]

tests/sys/net/if_ovpn/if_ovpn.sh

1063

Use atf_check?

You can do the same for ifconfig ovpn create by saving output to a file first, though that's a bit clunky.

[kp]

tests/sys/net/if_ovpn/if_ovpn.sh

1063

Yeah, I may as well.

The intent is to test for a bug I had in the preceding patch, which would cause a panic if we destroyed an ovpn interface that never had a socket attached. We don't need atf_check to detect that, but we might get other bugs that we would detect that way.
(Although atf_sh would already complain if we get a non-zero exit status from the test body, so it's more stylistic than functional in this case.)

[markj]

tests/sys/net/if_ovpn/if_ovpn.sh

1063

I'm inclined to do the same for the vnet.subr helpers. When reading kyua debug output, it's a bit easier to follow if commands use atf_check, since they get logged.

[kp]

Explicit atf_check

[markj]

tests/sys/net/if_ovpn/if_ovpn.sh

1063

I think it should be -s exit:0. I believe it can be omitted actually.

[kp]

*headdesk*