lxd/storage/drivers/volume: Switch to deviceConfig.DefaultVMBlockFilesystemSize
lxd/storage/drivers/volume: Switch to deviceConfig.DefaultVMBlockFilesystemSize

And remove DefaultVMBlockFilesystemSize constant.

Signed-off-by: Thomas Parrott <6b778ce645fb0e3dde76d79eccad490955b1ae74@canonical.com>

stgraber/lxd,stgraber/lxd,hallyn/lxd,stgraber/lxd,lxc/lxd,stgraber/lxd,hallyn/lxd,lxc/lxd,hallyn/lxd,lxc/lxd,lxc/lxd,hallyn/lxd,lxc/lxd,hallyn/lxd,stgraber/lxd,stgraber/lxd,stgraber/lxd,lxc/lxd,hallyn/lxd,lxc/lxd