[FIX] account_analytic_default: defaults on invoice when coming from SO

opw-2226421

The analytic accounts are not set on creation of a new invoice from a
Sale Order, and when they are set, the default should not override the
values selected on the SO.

This commit reverts what was done in be7d1d75
which basically reverted what was done in 69bf61bb

closes odoo/odoo#48793

X-original-commit: 02c75a70
Signed-off-by: Nicolas Martinelli (nim) <nim@odoo.com>