The chairman of the Senate Intelligence Committee, Richard Burr, has come under fire in recent weeks for unloading stock holdings right before the market crashed on fears of coronavirus and for a timely sale of shares in an obscure Dutch fertilizer company. Now the North Carolina Republican’s 2017 sale of his Washington, D.C., home to a group led by a donor and powerful lobbyist who had business before Burr’s committee is raising additional ethical questions. Burr sold the small townhouse, in the Capitol Hill neighborhood, for what, by some estimates, was an above market price — $900,000 — to a team led by lobbyist John Green.