Include allocated table memory in 'sh fib mem' output

Include allocated table memory in 'sh fib mem' output

DBGvpp# sh fib mem
FIB memory
  Tables:
             SAFI              Number   Bytes
         IPv4 unicast             2    673066
         IPv6 unicast             2    1054608
             MPLS                 1    4194312
        IPv4 multicast            2     2322
        IPv6 multicast            2      ???
  Nodes:
             Name               Size  in-use /allocated   totals
             Entry               96     20   /    20      1920/1920
         Entry Source            32      0   /    0       0/0
     Entry Path-Extensions       60      0   /    0       0/0
        multicast-Entry         192     12   /    12      2304/2304
           Path-list             40     28   /    28      1120/1120
           uRPF-list             16     20   /    20      320/320
             Path                72     28   /    28      2016/2016
      Node-list elements         20     28   /    28      560/560
        Node-list heads          8      30   /    30      240/240

Change-Id: I8c8f6f1c87502a40265bf4f302d0daef111a4a4e
Signed-off-by: Neale Ranns <nranns@cisco.com>