Don't close file descriptor number <whatever random garbage was on the

stack>.

Found by:	LLVM/Clang Static Checker
MFC after:	1 week

usr.bin/truncate/truncate.c

@@ -57,6 +57,7 @@ main(int argc, char **argv)
 	int	ch, error, fd, oflags;
 	char   *fname, *rname;
 
+	fd = -1;
 	rsize = tsize = 0;
 	error = 0;
 	rname = NULL;