[FIX] stock: same package in different location

- Create a move line from stock to shelf1 with PACK1
- Create a move line from stock to shelf2 with PACK1
- Validate

It should be be blocked. The contents of a package should all
be in the same location since the pack itself is in a location.

It's due to commit 78d6f46 that fix a rounding error.
However it should check for quants that have quantity since they
represents the package content.

closes odoo/odoo#41926

X-original-commit: c35ae635b58f205055621019c570a24d4ba98e33
Signed-off-by: Arnold Moyaux <amoyaux@users.noreply.github.com>