fix compilation error on i686
fix compilation error on i686

On 32 bit machines, size_t and uint64_t are different sizes.

Signed-off-by: Andy Grover <b7d524d2f5cc5aebadb6b92b08d3ab26911cde33@redhat.com>

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