SRINAGAR, April 20 -- Sam, Coco, Kiwi and Tuffy are the newest and th e youngest members of the Central Industrial Security Force's (CISF) canine unit. The four Labradors will now be trained to become explosive detectors to secure Delhi Metro. The three-month-old puppie s arrived at CISF's Delhi Metro Rail Corporation (DMRC) unit at Shastri Park about two weeks ago from a breeding centre near Kur- uskhetra in Haryana....