fix(reboot): ignore short uptime change before real reboot
fix(reboot): ignore short uptime change before real reboot

In one job, I found the `uptime -s` result increased 1 second without real
reboot, it might be caused by normal timedrift. So we should not treat it as
reboot finish if the uptime change is very short.

The uptime is the time kernel to start, so the normal time gap between two
uptime should contain system start time of first reboot, and the bios reset
time of second reboot. In the problem job, one complete reboot costed 3 mins
and 27 seconds.

The real gap time is effected many factors (instance type, system load, cloud
platform load, enabled services in system, etc), so here we just expect the gap
time is larger than 5 seconds.

This patch added a time gap check, it will ignore short uptime change before
real reboot.

Signed-off-by: Amos Kong <eb01d8f828a6c9a20be4534e72e049aaf41503df@scylladb.com>

scylladb/scylla-longevity-tests,scylladb/scylla-cluster-tests,scylladb/scylla-cluster-tests,scylladb/scylla-cluster-tests,scylladb/scylla-longevity-tests,scylladb/scylla-longevity-tests,scylladb/scylla-cluster-tests,scylladb/scylla-cluster-tests