To fix#406, I reverted the tmpfs mount we add at boot time. As we can
see in #455, it was a bad idea.
In addition to bringing back that mount, I've also added a
`tmpfs_mount_size` config that allows to change the size of the mount
from its default `2G`. It's also possible to disable the mount
altogether.
fixes#455
By looking at the code, it seems that it was a goal to make the sudo
wrapper path configurable through the Vagrantfile, but it wasn't
effective and didn't make much sense (that kind of config is a per-host
config, not a per-guest one).
This caused the cause to be needlessly complex by giving the Provider
the responsibility of instanciating the wrapper. This commit gets rid of
that.
I didn't get rid of `sudo_wrapper` injection in `Driver` and
`Driver::CLI` constructors because they're needed for tests. I'm not
ready to tackle this yet.
Sudoers now creates a safe wrapper script that performs sanity checks on sudo :
* wrapper generated in /usr/local/bin (name includes version to allow multiple wrappers on the same system)
* sudoers command now generates a one-line file in /etc/sudoers.d
* SudoWrapper use the new wrapper
* Removed unused Config#validate method
