This patch resolves a problem that may cause the CONTROL mbuf resources to 
not be freed and reused. This problem is evident by mbuf bucket#4 (size 256) 
utilisation constantly increasing and when the output of "vmstat -M" shows a 
'large' number for "Total bytes per type" IOBUF:
IO 0x4160 IO BUF 0xfffffffffffffe00 IORSRC 0x9090


