Apparently, “Bad Moms” was such a surprise hit (as if it was still a surprise that in 2016, there was a market for R-rated shock-comedies starring women) that the makers got Mila Kunis and everyone else back together to crank out a sequel in a little more than a year. Even better (as in not better), it’s Christmas themed. So we have “A Bad Moms Christmas” (2017) trying to catch lightning in a chimney. But whereas the original had just the right amount of mommy pathos, this one overdoes things (sequels always do) by pitting the moms against their moms.