Unable to have synced_folder with Fedora 22 VirtualBox

[aanm]

Not sure if it is related with #448 and #458 but every time I do a vagrant up I get this error message:

Failed to mount folders in Linux guest. This is usually because
the "vboxsf" file system is not available. Please verify that
the guest additions are properly installed in the guest and
can work properly. The command attempted was:

mount -t vboxsf -o uid=`id -u vagrant`,gid=`getent group vagrant | cut -d: -f3` vagrant /vagrant
mount -t vboxsf -o uid=`id -u vagrant`,gid=`id -g vagrant` vagrant /vagrant

The error output from the last command was:

/sbin/mount.vboxsf: mounting failed with the error: No such device

[cheeseplus]

Fixed @efeb14a810551b06d7c5718639034cd9d3b45219