Add an fstab nofail mount option and enable it by default except for / and /home

• nofail mounts won't prevent the system from booting if not mountable. systemd will still try to mount them in an asynchronous way, and add an error to the log if it fails.
• Most mount points, apart from / and /home should be mounted with nofail to prevent entering to recovery mode with a bootable system.
• partitionmanager doesn't remove fstab entries after removing a partition, which currently leads to recovery mode on the next boot. BUG: 472431

Enable nofail by default except when the mount point is / or /home

Apart from those, nofail mounts let the system boot normally. BUG: 476054