Fix symmetrization

Description

Fix some problem of numerical errors, that could lead to an out-of-bound exception. The check of the grid been compatible with the symmetries is now properly triggered by the variable SymmetrizeDensity and not the variable KPointsUseSymmetries.

News snippet

Improved stability for the symmetrization.

Checklist

• I have checked that my code follows the Octopus coding standards
• I have added tests for all the new features added in this request.