policy: kdbus_policy_set() make sure we restore the right entries

policy: kdbus_policy_set() make sure we restore the right entries

If kdbus_policy_set() fails we try to restore the entries that were
previously saved in a list, however due to a typo that logic was trying
to access a previously freed entry which will just break things...
So fix the typo 'l->e' instead of 'e'.

This fixes a bug triggered by test-kdbus-policy and makes the code able
to restore previously saved entries in case of errors.

Signed-off-by: Djalal Harouni <tixxdz@opendz.org>