revert 96e17fd: don't init pot_temp, frazil and age from restarts unt…

…il they are available - see COSIMA/initial_conditions_access-om2#2

ocean/field_table

@@ -12,17 +12,9 @@ restart_file  = ocean_temp_salt.res.nc
 ppm_hlimiter = 3
 ppm_vlimiter = 3
 /
-"diag_tracers","ocean_mod","pot_temp"
-const_init_tracer = .false.
-restart_file  = ocean_pot_temp.res.nc
-/
-"diag_tracers","ocean_mod","frazil"
-const_init_tracer = .false.
-restart_file  = ocean_frazil.res.nc
-/
 "tracer_packages","ocean_mod","ocean_age_tracer"
 names = global
-const_init_tracer = .false.
+const_init_tracer = .true.
 horizontal-advection-scheme = mdppm
 vertical-advection-scheme = mdppm
 ppm_hlimiter = 3