shelve: rename stripnodes to nodestoprune...
shelve: rename stripnodes to nodestoprune
Since we are introducing obs-based shelve, we are no longer
stripping temporary nodes, we are obsoleting them. Therefore
it looks like stipnodes would be a misleading name, while
prune has a connotaion of "strip but with obsolescense", so
nodestoprune seems like a good rename.