When using the rmr_realloc_payload() function with the copy
flag set, it was possible to copy a short length of data,
or none at all. This change corrects the miscomputed length
to copy.
Signed-off-by: E. Scott Daniels <daniels@research.att.com>
Change-Id: I01a98fa66ab69d5f11a792463bc04b73209f098b