Nearly an hour into the much-anticipated start to Eagles training camp, practice was blown dead with a blaring air horn and a screaming coach. There was plenty of energy in Wednesday’s inaugural session, and a low-intensity walkthrough was scheduled for the following day, but the Eagles were done, exactly 58 minutes after the start of practice. Relatively shorter practices aren’t new to this season; many of Eagles coach Nick Sirianni’s sessions during his first training camp last year were noticeably shorter than his predecessors’. The collective bargaining agreement allows NFL teams to hold o…