execvp() is (usually) equivalent to execvpe(), without enforcing any
change to the environment. However, unlike execvp(), execvpe() is not
standardized by POSIX, and may therefore not be available nor detected
when configuring the project (like on NetBSD).
No place could be found in fwknop to be using execvpe() and changing the
environment. Therefore it seems only logical (and safer) to use execvp()
instead.
This also updates the tests to reflect this change.
khorben
Michael Rash