Chris Coduto/Getty Images Undrafted rookie cornerback Keenan Garber, right, is signing with the Colts' practice squad. Xavien Howard’s abrupt retirement has forced the Indianapolis Colts into action at cornerback. Undrafted free agent Keenan Garber was signed to the Colts’ practice squad on Thursday, two days after Howard was surprisingly placed on the reserve/retired list. Garber, 25, spent training camp and the preseason with the Minnesota Vikings but was waived in August as part of final