BUG/MINOR: stats:Fix incorrect printf type.

The value is defined in include/types/global.h to be an unsigned int.
The type format in the printf is for a signed int. This eventually wraps
around.

WT: This bug was introduced in 1.5.
(cherry picked from commit b197d7f433fc126f754df3923761d2dcc0893f69)
1 file changed