fix: remove general use of load_block_as_user

For the config model we do not need to go as far as binding the block
to the user and already get enough data out of the modulestore to
satisfy the storage on the xblock case. Add a new function to get that
much xblock only.

For the limited cases where we are using the block more directly as a
block we maintain the old function.

Also includes a fix to test_views that was closing the wrong level
mock and leaving an open patch into other tests.