ping tests: Fix test on 32-bit platforms

[jlduran]

Summary

Actually use INT_MAX (0x7fffffff), not UINT_MAX (0xffffffff) to avoid
overflowing and missing the test.

Reported by:    Jenkins

Test Plan

The idea is to hit the test, not to overflow 32-bit architecture's time_t.
I do not have a 32-bit VM at the moment, would it be possible to run the test on ci.freebsd.org, and verify that test:
https://ci.freebsd.org/view/Test/job/FreeBSD-main-i386-test/17993/testReport/junit/sbin.ping.test_ping/py/TestPing__test_pinger__0_0_special_warp_/
Passes on i386?:

/usr/tests# kyua debug sbin/ping/test_ping.py:TestPing::test_pinger[_0_0_special_warp]

[markj]

I do not have a 32-bit VM at the moment, would it be possible to run the test on ci.freebsd.org, and verify that test:

Unfortunately there's no easy way to manually test patches using ci.freebsd.org yet. In the meantime I downloaded an i386 VM image and verified that the test passes.

[jlduran]

In D42268#964458, @markj wrote:

I do not have a 32-bit VM at the moment, would it be possible to run the test on ci.freebsd.org, and verify that test:

Unfortunately there's no easy way to manually test patches using ci.freebsd.org yet. In the meantime I downloaded an i386 VM image and verified that the test passes.

Thank you!

[markj]

Please submit a PR with the patch, or mail git format-patch output to me directly.