migration: report errors from criu or liblxc
migration: report errors from criu or liblxc

Signed-off-by: Tycho Andersen <10c18fcb898ee6b17d6575d444b125d10b3f4d6a@canonical.com>

lxc/lxd-pkg-ubuntu,lxc/lxd-pkg-ubuntu,lxc/lxd-pkg-ubuntu