Forget Walter White. Netflix may be “the one who knocks.” If there were any skepticism left about the clout the streaming service possesses, it may have been put to the rest Sunday after the AMC drama series “Breaking Bad” obliterated its own personal-best ratings by scoring 5.9 million total viewers– more than double the previous season premiere. That kind of growth spurt for a TV series doesn’t happen too often, and for that Netflix must have been a factor. Sure, AMC spent a handsome (and unspecified) amount to promote the series’ swan-song run, but marketing dollars alone can’t account for this kind of leap. Playing a bigger part could be the availability of an entire library of past seasons in the U.S. that enables curious new viewers to catch up and get funneled back to AMC for the new episodes.