By Erwin Seba and Nia Williams WASHINGTON, Kan. (Reuters) -Residents near the site of the worst U.S. oil pipeline leak in a decade took the commotion and smell in stride as cleanup crews labored in near-freezing temperatures, and investigators searched for clues to what caused the spill. A heavy odor of oil hung in the air as tractor trailers ferried generators, lighting and ground mats to a muddy site on the outskirts of this farming community, where a breach in the Keystone pipeline discovered on Wednesday spewed 14,000 barrels of oil. Pipeline operator TC Energy said on Friday it was evalua…