fix NSE+SDC when we are doing drive_initial_convection

[zingale]

The abar that we were getting was not consistent with NSE. Now we are sure to use the correct abar

[zingale]

this seems to fix the issues with the massive_star in the test suite. It does not change the convergence of nse_test (as expected):

 xmom                            1.383036e+28   1.897      3.714389e+27   1.835      1.041023e+27    1.741       3.11398e+26
 ymom                            1.383036e+28   1.897      3.714389e+27   1.835      1.041023e+27    1.741       3.11398e+26
 rho_E                           3.587648e+37   1.871      9.806645e+36   1.892      2.641936e+36    1.716      8.041602e+35
 rho_e                            3.53147e+37   1.873      9.640009e+36   1.891      2.599512e+36    1.714      7.925861e+35
 Temp                            7.094141e+20   2.076      1.682366e+20   1.920      4.446951e+19    1.906      1.186752e+19
 rho_He4                         3.006763e+18   2.003      7.500053e+17   1.913      1.992074e+17    1.936      5.206036e+16
 rho_Cr48                        1.641543e+19   2.192      3.592936e+18   2.071      8.549908e+17    1.983      2.162648e+17
 rho_Fe52                        4.609468e+19   1.891      1.243101e+19   1.850      3.447966e+18    1.973      8.784996e+17
 rho_Fe54                        4.238086e+20   2.230      9.031658e+19   2.160       2.02024e+19    2.157      4.529324e+18
 rho_Ni56                        4.415912e+20   2.244      9.321279e+19   2.160      2.085794e+19    2.128      4.771694e+18
 rho_n                           3.868686e+14   1.712      1.180947e+14   1.793      3.408363e+13    2.036      8.313224e+12
 rho_p                           8.873178e+17   2.230      1.891661e+17   1.851      5.242648e+16    1.768      1.539221e+16
 rho_Ye                          1.675925e+19   1.954      4.326574e+18   1.871      1.182975e+18    1.784      3.435075e+17
 rho_abar                        4.213351e+21   2.219      9.052191e+20   1.849      2.512485e+20    1.642      8.051212e+19
 rho_bea                         2.996564e+20   1.990      7.543645e+19   1.884      2.044339e+19    1.798      5.879044e+18
 rho_enuc                        2.036786e+39   1.156      9.137519e+38   1.102      4.258117e+38    0.951      2.203022e+38