lxd/instance/drivers/driver/lxc: Adds SaveConfigFile function
lxd/instance/drivers/driver/lxc: Adds SaveConfigFile function

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

hallyn/lxd,atxwebs/lxd,mjeanson/lxd,lxc/lxd,atxwebs/lxd,Skarlso/lxd,hallyn/lxd,stgraber/lxd,Skarlso/lxd,stgraber/lxd,lxc/lxd,mjeanson/lxd,mjeanson/lxd,stgraber/lxd,hallyn/lxd,lxc/lxd,hallyn/lxd,lxc/lxd,lxc/lxd,atxwebs/lxd,Skarlso/lxd,stgraber/lxd,lxc/lxd,atxwebs/lxd,stgraber/lxd,lxc/lxd,hallyn/lxd,stgraber/lxd,Skarlso/lxd,stgraber/lxd,hallyn/lxd