eCLM-PDAF related changes concerning cpl_inst_tag (HPSCTerrSys#46)

- PDAF: `cpl_inst_tag = ""` when `USE_PDAF` is true
- PDAF: add error message for unsupported `num_inst_driver > 1`
- use clear `#ifdef` inside single conditions
- add an error if `pdaf_id` or `pdaf_max` not present

src/eclm/cime_comp_mod.F90

@@ -658,16 +658,26 @@ subroutine cime_pre_init1(esmf_log_option)
     !   if (Global_comm /= MPI_COMM_NULL) then
 
     if (num_inst_driver > 1) then
+#ifdef USE_PDAF
+      call shr_sys_abort( subname//':: num_inst_driver > 1'// &
+        ' not supported for PDAF' )
+#else
        call seq_comm_init(global_comm, driver_comm, NLFileName, drv_comm_ID=driver_id)
        write(cpl_inst_tag,'("_",i4.4)') driver_id
-#ifdef USE_PDAF
-    else if (present(pdaf_id) .and. present(pdaf_max)) then
-       call seq_comm_init(global_comm, driver_comm, NLFileName, &
-                          pdaf_id=pdaf_id, pdaf_max=pdaf_max)
 #endif
     else
+#ifdef USE_PDAF
+      if (present(pdaf_id) .and. present(pdaf_max)) then
+        call seq_comm_init(global_comm, driver_comm, NLFileName, pdaf_id=pdaf_id, pdaf_max=pdaf_max)
+        cpl_inst_tag = ''
+      else
+        call shr_sys_abort( subname//':: pdaf_id and pdaf_max'// &
+          ' have to be present for PDAF' )
+      end if
+#else
        call seq_comm_init(global_comm, driver_comm, NLFileName)
        cpl_inst_tag = ''
+#endif
     end if
 
     !--- set task based threading counts ---