migration: add handler for CRIU feature checking
migration: add handler for CRIU feature checking

Now that lxc and go-lxc know about CRIU feature checking also start to
include feature checking in LXD.

Signed-off-by: Adrian Reber <9f82b3db7475afbb412180fe9fab7c69d6ece340@redhat.com>

lxc/lxd,stgraber/lxd,lxc/lxd,stgraber/lxd,stgraber/lxd,erikmack/lxd,hallyn/lxd,jsavikko/lxd,Skarlso/lxd,lxc/lxd,pcdummy/lxd,stgraber/lxd,atxwebs/lxd,lxc/lxd,stgraber/lxd,atxwebs/lxd,Skarlso/lxd,hallyn/lxd,hallyn/lxd,erikmack/lxd,stgraber/lxd,mjeanson/lxd,lxc/lxd,pcdummy/lxd,mjeanson/lxd,jsavikko/lxd,hallyn/lxd,lxc/lxd,mjeanson/lxd,jsavikko/lxd,erikmack/lxd,hallyn/lxd,pcdummy/lxd,lxc/lxd,Skarlso/lxd,Skarlso/lxd,atxwebs/lxd,hallyn/lxd,stgraber/lxd,atxwebs/lxd