test/format failure due to casting of lseek return value

The Jenkins job at http://build.wiredtiger.com:8080/job/wiredtiger-test-format-stress/73632/console failed because of the test programs use of the error_sys_check macro for lseek.

The failure message is:

t: FAILED: copy_blocks/269: lseek(rfd, (wt_off_t)offset, SEEK_SET): error return: -2140901376

But the real problem is that (on the AWS Linux) lseek returns an off_t which is 8 bytes and the error_sys_check casts the return value of a system call to int which is 4 bytes. This fails once the offset goes above 2Gb.