ewaol-distro/k3s: Disable SC2086 shellcheck for k3s-killall.sh

Recent updates in host tools detected new shellcheck failures in k3s-killall.sh
Since they are not critical, lets ignore them.

Issue-Id: SCM-3910
Signed-off-by: Diego Sueiro <diego.sueiro@arm.com>
Change-Id: Ic5869e6584ff9a447dede184650a489fe43adc91