four new netconf mounts using same schema not sharing same compiled schema

It seems that when simultaneously mounting up to four identical devices, they will all be
compiled and kept in memory even though they can share the same compiled yang models.

If you first add a single device and wait for it to be full connected (thus, compiled/mounted), the
remaining devices that are mounted will reuse the already compiled models.

Also, if you attempt to simultaneously mount 5+ devices, it's only the first four that are
duplicated and anything after the 4th will share.

This may be expected behavior, but with a large compiled schema, you can quickly create
a case where lots of heap is used and can get to an OOM condition.