lib,ospfd: support table-direct in OSPFv2

[rzalamena]

This PR does two things:

1. Fixes the generation of the redistribute methods string to not include table and table-direct automatically. These two redistribute methods require an argument which is the table ID so they can not be mixed with other redistribution types.

   Example of broken command:

    DEFUN (ospf_redistribute_source,                                                                                                                                                             
         ospf_redistribute_source_cmd,                                                                                                                                                         
         "redistribute " FRR_REDIST_STR_OSPFD " [{metric (0-16777214)|metric-type (1-2)|route-map RMAP_NAME}]",                                                                                
         REDIST_STR                                                                                                                                                                            
         FRR_REDIST_HELP_STR_OSPFD                                                                                                                                                             
         "Metric for redistributed routes\n"                                                                                                                                                   
         "OSPF default metric\n"                                                                                                                                                               
         "OSPF exterior metric type for redistributed routes\n"                                                                                                                                
         "Set OSPF External Type 1/2 metrics\n"                                                                                                                                                
         "Route map reference\n"                                                                                                                                                               
         "Pointer to route-map entries\n")
   
   // Where:
   #define FRR_REDIST_STR_OSPFD \                                                                                                                                                                 
     "<kernel|connected|local|static|rip|isis|bgp|eigrp|nhrp|table|vnc|babel|sharp|openfabric|table-direct>"

   (the command is broken because redistribute table or redistribute table-direct won't work as is)

2. Add support for table-direct in OSPFv2 by reusing the DEFUN of redistribute table (both take the same integer argument with the same limits).

[riw777]

Can you give before and after examples of redistribution? Sorry, just having a problem visualizing what this is doing ...