Re: A couple of random BF failures in kerberosCheck

I wrote:
> * kerberos/t/001_auth.pl just blithely assumes that it can pick
> any random port above 48K and that's guaranteed to be free.
> Maybe we should split out the code in get_new_node for finding
> a free TCP port, so we can call it here?

I've confirmed that the reason it's failing on my machine is exactly
that krb5kdc tries to bind to a socket that is still in TIME_WAIT state.
Also, it looks like the socket is typically one that was used by the
GSSAPI client side (no surprise, the test leaves a lot more of those
than the one server socket), so we'd have no record of it even if we
were somehow saving state from prior runs.

So I propose the attached patch, which seems to fix this for me.

The particular case I'm looking at (running these tests in a tight
loop) is of course not that interesting, but I argue that it's just
increasing the odds of failure enough that I can isolate the cause.
A buildfarm animal running both kerberos and ldap tests is almost
certainly at risk of such a failure with low probability.

(Still don't know what actually happened in those two buildfarm
failures, though.)

regards, tom lane