sentinalmap: make a few methods static + public
sentinalmap: make a few methods static + public

Mostly for unit testing, but the static helps regardless

plasma-umass/DoubleTake,bpowers/DoubleTake,plasma-umass/DoubleTake,plasma-umass/DoubleTake,bpowers/DoubleTake,bpowers/DoubleTake,bpowers/DoubleTake,plasma-umass/DoubleTake,plasma-umass/DoubleTake,bpowers/DoubleTake,bpowers/DoubleTake,bpowers/DoubleTake,plasma-umass/DoubleTake,bpowers/DoubleTake,plasma-umass/DoubleTake