Work around PHP bug in new PHPs.

https://github.com/php/php-src/commit/6408a1a59e6d371cd488687e28e18815ea97984e#diff-258cc1cabc37df15d7f0ed40924f64efR283 started copying all nodes, breaking references to parent elements and the like.

This represents a somewhat more direct workaround for what is _actually_ being addressed in https://github.com/discoverygarden/islandora_solution_pack_manuscript/pull/35.