update(systemd): add falco.service alias to all systemd units

[ekoops]

What type of PR is this?

/kind feature

Any specific area of the project related to this PR?

/area engine

What this PR does / why we need it:

This PR allows to refer to the engine systemd services with a consistent unique alias falco.service. In addition, the alias systemd system helps to prevent from running more than one Falco instance with systemd at the time, since it is not possible to enable two systemd service, with the same alias, at the same time.

Which issue(s) this PR fixes:

Fixes #

Special notes for your reviewer:

Does this PR introduce a user-facing change?:

update(systemd): users can refer to systemd falco services with a constistent unique alias falco.service

[poiana]

Welcome @ekoops! It looks like this is your first PR to falcosecurity/falco 🎉

[FedeDP]

Very nice fix, thank you!
cc @Andreagit97 that worked a lot with me on the systemd units :)

/milestone 0.39.0

[ekoops]

As you can see, systemd doesn't allow to enable multiple services having the same alias:

vagrant@vagrant:/etc/systemd/system$ sudo systemctl daemon-reload
vagrant@vagrant:/etc/systemd/system$ cat test.service | grep Alias
Alias=t.service
vagrant@vagrant:/etc/systemd/system$ cat test2.service | grep Alias
Alias=t.service
vagrant@vagrant:/etc/systemd/system$ sudo systemctl enable test.service
vagrant@vagrant:/etc/systemd/system$ sudo systemctl enable test2.service
Failed to enable unit: File /etc/systemd/system/t.service already exists and is a symlink to /etc/systemd/system/test.service.
vagrant@vagrant:/etc/systemd/system$ sudo systemctl enable t.service
Failed to enable unit: Refusing to operate on alias name or linked unit file: t.service

[FedeDP]

/approve

[poiana]

LGTM label has been added.

Git tree hash: 0105b25c4b0349fe68769a9a7ee9bcb182877f80

[Andreagit97]

/approve

[poiana]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: Andreagit97, ekoops, FedeDP

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