Add panic_on_unrecovered_nmi to kernel settings (#7837)

Watchdog does not trigger a kernel panic on Arista 7170 platform because this parameter is missing on 201911 but not on master.

Author: zzhiyuan

build_debian.sh

@@ -382,6 +382,7 @@ sudo augtool --autosave "
 set /files/etc/sysctl.conf/kernel.core_pattern '|/usr/bin/coredump-compress %e %t %p %P'
 set /files/etc/sysctl.conf/kernel.softlockup_panic 1
 set /files/etc/sysctl.conf/kernel.panic 10
+set /files/etc/sysctl.conf/kernel.panic_on_unrecovered_nmi 1
 set /files/etc/sysctl.conf/vm.panic_on_oom 2
 set /files/etc/sysctl.conf/fs.suid_dumpable 2
 " -r $FILESYSTEM_ROOT