Fix OEP full - spin polarized case

Description

The OEP full was not taking the right occupations for the spin-polarized case.

News snippet

The OEP full was not taking the right occupations for the spin-polarized case.

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.

testsuite/finite_systems_3d/07-spin_orbit_coupling.test

@@ -53,7 +53,7 @@ Processors: 1
 Input: 07-spin_orbit_coupling.01-hgh-elpa.inp
 if(available scalapack); then
   if(available ELPA); then
-    Precision: 1e-8
+    Precision: 1e-5
     match ; SCF convergence ; GREPCOUNT(static/info, 'SCF converged') ; 1
     match ;  Eigenvalue  1  ; GREPFIELD(static/info, ' 1   --', 3) ; -27.437676
     match ;  Eigenvalue  3  ; GREPFIELD(static/info, ' 3   --', 3) ; -26.544792