Allow to define pre-start and post-stop tasks

WHile you can leverage config_overrides for that, it might become
tricky if you need to define more then 1 pre/post exec tasks.

Change-Id: I3d8b36f5e9f4be89eaff848d8ba88a38ce5285e4

defaults/main.yml

@@ -102,8 +102,10 @@ systemd_environment: {}
 #  can contain the following options:
 #  `service_name` -- (required) used to define the name of the service. This is typically the name of the executable.
 #  `service_type` -- (optional) Set the service type, default is "simple".
+#  `execstartpres` -- (optional) Set the program that wil lexecute before service startup.
 #  `execstarts` -- (required) Set the program to start, when the service is simple the list has a max length of 1.
 #  `execstops` -- (optional) Set the program to stop, when the service is simple the list has a max length of 1.
+#  `execstopposts` -- (optional) Set the program that wil lexecute after service stop.
 #  `after_targets` -- (optional) Start the service after this list of dependency units.
 #  `partof` -- (optional) Set the systemd "partof" directive. This ties a service unit to another.
 #  `config_overrides` -- (optional) This allows any section or key=value pair to be set within the systemd unit file.
@@ -198,6 +200,8 @@ systemd_environment: {}
 #       execstops
 #         - /usr/bin/stopcmd1
 #         - /usr/bin/stopcmd2
+#       execstopposts:
+#         - /usr/local/bin/hook
 #       sockets:
 #         - socket_name: SocketServiceZ
 #           after_targets:

releasenotes/notes/systemd_service_pre_post_exec-283b657e52d33d2b.yaml

@@ -0,0 +1,6 @@
+---
+features:
+  - |
+    Now you can define ``execstartpres`` and ``execstopposts`` keys for the
+    `systemd_services` structure. They will allow to define pre-start and
+    post-stop service executables and must be defined as lists.

templates/systemd-service.j2

@@ -32,6 +32,10 @@ Environment="{{ key }}={{ value }}"
 EnvironmentFile={{ item.environment_file | default(systemd_environment_file) }}
 {% endif %}
 
+{% for execstartpre in item.execstartpres | default([]) %}
+ExecStartPre={{ execstartpre }}
+{% endfor %}
+
 {% set _execstarts = item.execstarts %}
 {% if _execstarts is string %}
 {%   set _execstarts = [_execstarts] %}
@@ -56,6 +60,10 @@ ExecReload={{ execreload }}
 ExecStop={{ execstop }}
 {% endfor %}
 
+{% for execstoppost in item.execstopposts | default([]) %}
+ExecStopPost={{ execstoppost }}
+{% endfor %}
+
 # Give a reasonable amount of time for the server to start up/shut down
 TimeoutSec={{ systemd_TimeoutSec }}
 {% if service_type != 'oneshot' %}