Update native watchdog to be triggered after 20 restarts instead of 4.

The native watchdog performs a complete reboot on 5 system server
restarts even before packageWatchdog/RescueParty can perform any of the
mitigations. Increasing the thrsehold at which native watchdog kicks in
to 20 instad of 4.

Test: manual
Bug: 291137901
Change-Id: I9166f6555020e8bf26cc86994b13c53745a9934b