Fix self-tests in poudriere, make them more robust [1].

The self-tests used to fail in poudriere with dependency cycles in
Makefile that weren't visible earlier. Conditionally change ALL_TARGET
to check (do not use all check, that would require gmake) if the TEST
option is set (default), or set TEST_TARGET if the TEST option is unset.

While I am unable to reproduce 212146 claiming the self-tests fail on an
IPv6-disabled host, and I believe it's a red herring masking a local
configuration issue, doubt sed(1) and add blanks, and be sure to add the
"proto" earlier. The reporter didn't mention his OS version.

No PORTREVISION bump since the default build is unaffected.

PR: 212146 [1]