Make the periodic_systems/25-Fe_polarized more stable.

Description

Make the periodic_systems/25-Fe_polarized more stable. Now the two magnetic moments are almost identical, as they should.

Before:

Local Magnetic Moments (sphere radius [b] =   2.337):
 Ion                    mz
   1        Fe       0.528189
   2        Fe       0.473072

After:

Local Magnetic Moments (sphere radius [b] =   2.337):
 Ion                    mz
   1        Fe       2.756780
   2        Fe       2.756780

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.