tcmu-runner:Fix the possible the memory overflow.
tcmu-runner:Fix the possible the memory overflow.

Set the 'fix' buffer length to 64-byte CDBs, this works fine
usually. And if the variable CDB bytes is larger than 64 bytes,
then will use the new buf.

Signed-off-by: Xiubo Li <67e5e1ee902b4e67bce18ea43d9c4b0430ce5e6c@cmss.chinamobile.com>

agrover/tcmu-runner,superlibj/tcmu-runner,lxbsz/tcmu-runner,open-iscsi/tcmu-runner,JefferyHu/tcmu-runner,open-iscsi/tcmu-runner,liuy/tcmu-runner