server: fix close of "policy_server.dat" after poking it

In KeepHardClasses() we attempt to fopen("policy_server.dat") just
to prove it's readable.

We have to close it, too. We are not in C++, guys..
(cherry picked from commit a4a4442277702fb0b4b05ea3197bfe2b9814752a)

Conflicts:

	src/cf-serverd-functions.c