Fix the restart of DFT+U.

Description

Fix the restart of DFT+U. The old version was leading to imprecise restarting as data where not read in binary but recomputed.

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.

src/td/td.F90

@@ -841,10 +841,12 @@ contains
       if (from_scratch) call states_elec_fermi(st, namespace, gr%mesh)
     end if
 
-    ! Initialize the occupation matrices and U for LDA+U
-    ! This must be called before parsing TDFreezeOccupations and TDFreezeU
-    ! in order that the code does properly the initialization.
-    call lda_u_update_occ_matrices(hm%lda_u, namespace, gr%mesh, st, hm%hm_base, hm%energy)
+    if (from_scratch) then
+      ! Initialize the occupation matrices and U for LDA+U
+      ! This must be called before parsing TDFreezeOccupations and TDFreezeU
+      ! in order that the code does properly the initialization.
+      call lda_u_update_occ_matrices(hm%lda_u, namespace, gr%mesh, st, hm%hm_base, hm%energy)
+    end if
 
     if (freeze_orbitals > 0) then
       if (from_scratch) then
@@ -1193,9 +1195,14 @@ contains
 
     ! read potential from previous interactions
     call potential_interpolation_load(td%tr%vksold, namespace, space, restart, gr%mesh, st%d%nspin, err2)
-
     if (err2 /= 0) ierr = ierr + 2
 
+    if (hm%lda_u_level /= DFT_U_NONE) then
+      call lda_u_load(restart, hm%lda_u, st, hm%energy%dft_u, ierr)
+      if (err /= 0) ierr = ierr + 1
+    end if
+
+
     ! read PES restart
     if (td%pesv%calc_spm .or. td%pesv%calc_mask .or. td%pesv%calc_flux) then
       call pes_load(td%pesv, namespace, restart, st, err)