streamCopy() should return proper structure.

Callers of streamCopy() expect an array to be returned containing count and result.

Conflicts:
	lib/helper.php
	tests/lib/helper.php
Merge pull request #5343 from owncloud/backport-5340-stable5

Backport 5340 stable5

* owncloud/backport-5340-stable5:
  streamCopy() should return proper structure.