Commercial mortgage lender Walker & Dunlop made an inauspicious debut on the New York Stock Exchange last week as its shares closed below the initial-public-offering price, but the showing may say more of the tempering IPO market than the strength of the offering. The Bethesda firm’s stock, with an initial per-share price of $10, hovered around $9.80 for much of the day and closed at $9.90. Shares were priced well below the $14 to $16 range that Walker & Dunlop anticipated in its Securities and Exchange Commission filing on Dec. 13.