Close spamd socket when we're finished with it

QP's connection to spamd unnecessarily persists beyond the run of the
spamassassin plugin itself.  This closes the socket as soon as we're
finished using it.

Signed-off-by: Ask Bjørn Hansen <ask@develooper.com>

Changes

@@ -1,3 +1,5 @@
+  Close spamd socket after reading the result back (Jared Johnson)
+
   p0f plugin updates (Tom Callahan)
 
   Change transaction->add_recipient to skip adding "null" rcpt if passed

plugins/spamassassin

@@ -189,6 +189,7 @@ sub hook_data_post { # check_spam
 
   }
   my $tests = <SPAMD>;
+  close SPAMD;
   $tests =~ s/\015//;  # hack for outlook
   $flag = $flag eq 'True' ? 'Yes' : 'No';
   $self->log(LOGDEBUG, "check_spam: finished reading from spamd");