Qdoba, a food court staple here for most of the past decade, has cashed in its tortilla chips at Westfield Montgomery Mall. The closing comes almost exactly a year after the arrival of Mexican juggernaut Chipotle, one of the most popular additions to the mall’s recently renovated Dining Terrace. Chipotle, which appears to be on the comeback trail after its recent food safety scare, will now have the mall’s black-bean-and-burrito crowd to itself. Qdoba fans can visit the chain’s Rockville restaurant on Rollins Avenue.