Sprint’s owner, Softbank of Japan, is standing by its troubled US child, with founder Masayoshi Son saying that Sprint’s radical capex cuts helped boost its parent’s operating margins by 8.8% in its just-finished fiscal year. “Cost cutting is going smoothly at Sprint,” said Son during an analyst call. “We’ll see a V-shaped recovery.” However, his comments did not reassure some analysts. For one thing, Softbank’s operating profit may have improved, but it missed analyst expectations, and the Japanese firm did not offer guidance for the current fiscal year, saying there were too many uncertainties. For another, Sprint is still heavily dependent on loans from its parent and elsewhere to continue its 4G build-out and its densification program, which is nevertheless likely…