poh: fix rare hang

When the pack->bank link is unreliable, banks will in rare cases get
overrun on their next microblock, if they take too long between when
they release the fseq account lock, and then poll for the next
fragment.  This is not OK, both because the accounts in the next
microblock will get locked indefinitely (and the bank will be locked
forever), but also PoH will not see the transaction count it expected
from pack and will hang forever.

src/app/fdctl/config.c

@@ -696,12 +696,8 @@ topo_initialize( config_t * config ) {
      will never send more than one leader message until the pack tile
      must acknowledge it with a packing done frag, so there will be at
      most one in flight at any time. */
-  /**/                 fd_topob_tile_in(  topo, "pack",    0UL,          "metric_in", "poh_pack",     0UL,          FD_TOPOB_UNRELIABLE, FD_TOPOB_POLLED );
-  /* These pack to bank links are reliable, but they are flow controlled
-     by the busy flag that sits between them.  We don't mark them
-     reliable here because it creates a reliable link loop (poh -> pack
-     -> bank) which leads to credit starvation. */
-  FOR(bank_tile_cnt)   fd_topob_tile_in(  topo, "bank",   i,             "metric_in", "pack_bank",    0UL,          FD_TOPOB_UNRELIABLE, FD_TOPOB_POLLED );
+  /**/                 fd_topob_tile_in(  topo, "pack",   0UL,           "metric_in", "poh_pack",     0UL,          FD_TOPOB_UNRELIABLE, FD_TOPOB_POLLED );
+  FOR(bank_tile_cnt)   fd_topob_tile_in(  topo, "bank",   i,             "metric_in", "pack_bank",    0UL,          FD_TOPOB_RELIABLE,   FD_TOPOB_POLLED );
   FOR(bank_tile_cnt)   fd_topob_tile_in(  topo, "poh",    0UL,           "metric_in", "bank_poh",     i,            FD_TOPOB_RELIABLE,   FD_TOPOB_POLLED );
   /**/                 fd_topob_tile_in(  topo, "poh",    0UL,           "metric_in", "stake_out",    0UL,          FD_TOPOB_RELIABLE,   FD_TOPOB_POLLED );
   /**/                 fd_topob_tile_in(  topo, "poh",    0UL,           "metric_in", "pack_bank",    0UL,          FD_TOPOB_RELIABLE,   FD_TOPOB_POLLED );