Force container deletion if namespace does not exist in service_kill

When a service is stopped using "service_kill" script and the
namespace where the container is running does not exist, the
container processi should be forced to stop from the root namespace.

A namespace where a process is running, can be deleted whitout
stopping the mentioned process. "ip netns identify <PID>" then
returns an empty string (root namespace).

This patch will prevent an endless loop in Neutron DHCP agent. As
reported in the related bug, when a DHCP agent is resync, the DHCP
helper (metadata proxy) is stopped. In case this process stop raises
an exception (for example if the namespace does not exist), schedules
again a resync, creating an endless loop.

Change-Id: I9bac918fcde80e6a2336bc3cf1e6972512298118
Closes-Bug: #1868607
(cherry picked from commit c516df9e51)

tripleo_ansible/roles/tripleo-systemd-wrapper/templates/service_kill.j2

@@ -17,13 +17,13 @@ SIG=$1
 PID=$2
 NETNS=$(ip netns identify ${PID})
 
-if [ "x${NETNS}" == "x" ]; then
-  add_date "No network namespace detected, exiting"
-  exit 1
-fi
-
 {% if tripleo_systemd_wrapper_container_cli == 'podman' %}
-CLI="nsenter --net=/run/netns/${NETNS} --preserve-credentials -m -t 1 podman"
+if [ "x${NETNS}" == "x" ]; then
+  CLI="podman"
+  SIG=9
+else
+  CLI="nsenter --net=/run/netns/${NETNS} --preserve-credentials -m -t 1 podman"
+fi
 {% elif tripleo_systemd_wrapper_container_cli == 'docker' %}
 {% if tripleo_systemd_wrapper_docker_additional_sockets and tripleo_systemd_wrapper_docker_additional_sockets|length > 0-%}
 export DOCKER_HOST=unix://{{ tripleo_systemd_wrapper_docker_additional_sockets[0] }}