Merge PR# 1515 'Larofeticus/fix_config_pool_leak' into develop

According to comment in #1501 config_pool entries created in halo
exchanges are no longer used and can be removed. Config_pool entries
when ported to halo data structure reuse also cause a memory leak.

According to comment in #1502 the code builds and passes testing.

src/framework/mpas_dmpar.F

@@ -6800,8 +6800,6 @@ subroutine mpas_dmpar_exch_group_add_field(domain, groupName, fieldName, timeLev
          do while (associated(exchGroupPtr))
             if ( nLen == exchGroupPtr % nLen) then
                if ( groupName(1:nLen) == exchGroupPtr % groupName(1:exchGroupPtr % nLen) ) then
-                  call mpas_pool_add_config(exchGroupPtr % fieldPool, fieldName, timeLevelLocal)
-
                   ! Add field to exchange group's fieldList
                   if ( associated(exchGroupPtr % fieldList) ) then
                      ! If the field is already added, find it.
@@ -6923,9 +6921,6 @@ subroutine mpas_dmpar_exch_group_remove_field(domain, groupName, fieldName, iErr
          do while (associated(exchGroupPtr))
             if ( nLen == exchGroupPtr % nLen) then
                if ( groupName(1:nLen) == exchGroupPtr % groupName(1:exchGroupPtr % nLen) ) then
-                  ! Remove after the transition to exchange_field_lists is complete
-                  call mpas_pool_remove_config(exchGroupPtr % fieldPool, fieldName)
-
                   if ( associated(exchGroupPtr % fieldList) ) then
                      exchFieldListPtr => exchGroupPtr % fieldList
                      nullify(prevFieldListPtr)
@@ -7320,8 +7315,6 @@ subroutine mpas_dmpar_exch_group_reuse_halo_exch(domain, groupName, timeLevel, h
                   else
                     exchFieldListPtr % haloLayers(:) = .true.
                   end if
-                  call mpas_pool_remove_config(exchGroupPtr % fieldPool, exchFieldListPtr % fieldName)
-                  call mpas_pool_add_config(exchGroupPtr % fieldPool, exchFieldListPtr % fieldName, timeLevelLocal)
                   exchFieldListPtr => exchFieldListPtr % next
                 end do
               end if