Advection schemes cause trd_trc to be called when key not set

[timgraham]

When running with passive tracers (using my_trc) and key_trdtra but not key_trdtrc the advection scheme (I'm using tvd but all others are the same) calls trd_mod when it is handling the passive tracers. trd_mod then calls trd_mod_trc resulting in the following print statements in the output files.

trd_mod_trc_trp : You should not have seen this print! error?

This is due to the variable l_trd being set within the initial if statement:

      IF( kt == kit000 )  THEN
         IF(lwp) WRITE(numout,*)
         IF(lwp) WRITE(numout,*) 'tra_adv_tvd : TVD advection scheme on ', cdtype
         IF(lwp) WRITE(numout,*) '~~~~~~~~~~~'
         !
         l_trd = .FALSE.
         IF( ( cdtype == 'TRA' .AND. l_trdtra ) .OR. ( cdtype == 'TRC' .AND. l_trdtrc ) ) l_trd = .TRUE.
      ENDIF

I propose fixing this by moving the last two lines outside of the IF block so that l_trd is updated each time the advection scheme is called. i.e.

      IF( kt == kit000 )  THEN
         IF(lwp) WRITE(numout,*)
         IF(lwp) WRITE(numout,*) 'tra_adv_tvd : TVD advection scheme on ', cdtype
         IF(lwp) WRITE(numout,*) '~~~~~~~~~~~'
      ENDIF
      !
      l_trd = .FALSE.
      IF( ( cdtype == 'TRA' .AND. l_trdtra ) .OR. ( cdtype == 'TRC' .AND. l_trdtrc ) ) l_trd = .TRUE.

Unless I hear otherwise I intend to implement this change on Monday (17th Feb).

[timgraham]

Code committed to dev_MERGE_2013 branch in revision 4499