unix tests: Skip random_eor_and_waitall unconditionally

This test always fails, I don't see any reason to make it conditional on
the "CI" test parameter.

There is at least one test bug here, we're using the wrong sysctl to
obtain the receive buffer size, but fixing that is not sufficient.

PR: 279354
Reviewed by: glebius
MFC after: 1 week
Differential Revision: https://reviews.freebsd.org/D46726