Do not make boot process or activation wait or fail on non-critical services

[ibizaman]

Non-critical services for the activation or boot process are at least:

• backups
• VPNs

Those services, although necessary for the correct behavior of a server, should not stall the boot process or activation.

[ibizaman]

From https://bbs.archlinux.org/viewtopic.php?id=279681 we can use systemd-analyze critical-chain to try to fix this.