Automatic restart of tomcat like it was on AL1

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**Tell us about your request**
Since migration from AL1 to AL2 we have lost the automatic restart of Tomcat service in case of crash.
Previously when tomcat crashes, it was auto-restarted by monit. This is no longer the case in AL2.

**Is this request specific to an Elastic Beanstalk [platform](https://docs.aws.amazon.com/elasticbeanstalk/latest/platforms/platforms-supported.html)?**
Yes - Tomcat

**Tell us about the problem you're trying to solve. What are you trying to do, and why is it hard?**
When tomcat crashes, the application is no longer available. Beanstalk console shows a simple message: "Tomcat service not started"

**Are you currently working around this issue?**
I tried to add "Restart=always" in file /etc/systemd/system/tomcat.service.d/tomcat.conf using .ebextensions, but unfortunately there is no hook between the configuration file creation and the start of tomcat

**Additional context**
With linux 1 we had file /etc/monit.d/monit-tomcat8.conf with content

```
# Beanstalk Supported

# http support
set daemon 30
set httpd port 2812 and
use address localhost
allow localhost

#tomcat
check process tomcat with pidfile /var/run/tomcat8.pid
start program = "/etc/init.d/tomcat8 start"
stop program = "/etc/init.d/tomcat8 stop"
```

Now with AL2 we have /etc/systemd/system/tomcat.service.d/tomcat.conf with content

```
[Unit]
PartOf=aws-eb.target

[Service]
ExecStartPost=/bin/sh -c "systemctl show -p MainPID tomcat.service | cut -d= -f2 > /var/pids/tomcat.pid"
ExecStopPost=/bin/sh -c "rm -f /var/pids/tomcat.pid"
```

We should add this line in this file to enable automatic restart:

`Restart=always`

Start with /etc/systemd/system/tomcat.service.d/tomcat.conf and compare its current [Service] settings with the requested systemd behavior. The work is done when the configuration enables automatic Tomcat restart after a crash and the AL2 Tomcat platform starts with that setting applied.

Written by the indexing model from the issue text.