PHOENIX — The Padres worked and worked before it ultimately worked for them. They created scoring opportunities against Zac Gallen in the first two innings Saturday before he seemed to be about to do what many of the best pitchers do and find their footing. But the Padres kept to their commitment to remain disciplined but aggressive. And in the fourth inning, they did more than create opportunity, scoring twice and then holding on for a 2-0 victory over the Diamondbacks on Saturday night at Chase Field. Joe Musgrove allowed four hits over six innings and earned his 10th win of the season. Nick…