test/nstool: Fix fd leak in accept() loop

nstool loops on accept(), but failed to close the accepted socket fds
before continuing on.  So, with repeated commands it would eventually die
with an EMFILE.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>

test/nstool.c

@@ -201,6 +201,8 @@ static void cmd_hold(int argc, char *argv[])
 		rc = read(afd, &buf, sizeof(buf));
 		if (rc < 0)
 			die("read(): %s\n", strerror(errno));
+
+		close(afd);
 	} while (rc == 0);
 
 	unlink(sockpath);