[baseimage] kernel oom-killer to panic when the system is truly out o…

…f memory (#2988)

- What I did
Currently when the system is under memory pressure, the OOM killer kicks in and kills a rogue process. Killing a rogue process can cause the device to be un-healthy leading to blackholing of the traffic.

To avoid this, configure the OOM to do a kernel panic which will cause the device to reboot and come back up healthy.

- How I did it
Added the sysctl variable panic_on_oom and set the value to 2.
Setting it to 2 will ensure OOM killer to always do a kernel panic.

build_debian.sh

@@ -282,6 +282,7 @@ set /files/etc/sysctl.conf/kernel.core_pattern '|/usr/bin/coredump-compress %e %
 
 set /files/etc/sysctl.conf/kernel.softlockup_panic 1
 set /files/etc/sysctl.conf/kernel.panic 10
+set /files/etc/sysctl.conf/vm.panic_on_oom 2
 set /files/etc/sysctl.conf/fs.suid_dumpable 2
 
 set /files/etc/sysctl.conf/net.ipv4.conf.default.forwarding 1