Remove getty and udev targets to lower CPU usage

[sblaisot]

Remove systemd's getty and udev targets to lower CPU usage when using containers

[myii]

@sblaisot I like the idea behind this because I've suffered from this previously. I'm finding I'm short on time to test this at the moment, though. I reckon we could go ahead and merge it, since it seems fine from an eyeball review. What do you think, @javierbertoli?

[javierbertoli]

Agreed. I left it opened to extend the idea to the other distros too, but I'm short of time too.

@sblaisot would you dare extend it to the other distros too? After all, if something breaks, we can find out with the tests and revert.

If you prefer not to do it, we might just add a ticket to remember doing it in the future.

[myii]

Merging this now so that #29 can be merged cleanly, which is further going to be extended with the OpenSUSE workaround. I'll make an issue for getty on the other platforms.