[Swan-dev] Generate test certificates iff missing

[Andrew Cagney]

I'd like to change testing/pluto/Makefile so that "make check" will
generate the certificates iff they are missing (or to be precise, if
the certificate testing/x509/keys/mainca.key is missing).

- to generate the certificates it will use EAST (although as Matt
pointed out it should probably technically use NIC)

- it will only generate the certificates if they are missing; i.e.,
second and further "make check" won't generate new certificates

- or to put it the other way, it won't re-generate the certificates if
they are out-of-date (dist_certs.py newer than mainca.key)

- this does assume that you VM is less than 3 months old

As an alternative we could:

- have "make check" depend on mainca.key; and define manca.key's rule
to barf with a message about how to fix the problem

>From my pov "make check" should set everything up as needed; and
having it bumble on when there are no certificates is infuriating.

Andrew