migration: fix tempdir handling
migration: fix tempdir handling

If we fail to create the tempdir, we don't need to delete it. We *do*
however, need to inform the main thread that the restore failed.

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

stgraber/lxd,atxwebs/lxd,georghopp/lxd,chrisglass/lxd,erikmack/lxd,hallyn/lxd,chrisglass/lxd,Skarlso/lxd,akshaykarle/lxd,lxc/lxd,jsavikko/lxd,mjeanson/lxd,hallyn/lxd,Skarlso/lxd,ollie314/lxd,mjeanson/lxd,jsavikko/lxd,mjeanson/lxd,pcdummy/lxd,Skarlso/lxd,hallyn/lxd,akshaykarle/lxd,techtonik/lxd,atxwebs/lxd,stgraber/lxd,pcdummy/lxd,chrisglass/lxd,ollie314/lxd,atxwebs/lxd,lxc/lxd,lxc/lxd,stgraber/lxd,lxc/lxd,atxwebs/lxd,stgraber/lxd,hallyn/lxd,hallyn/lxd,techtonik/lxd,erikmack/lxd,stgraber/lxd,lxc/lxd,akshaykarle/lxd,ollie314/lxd,georghopp/lxd,techtonik/lxd,hallyn/lxd,lxc/lxd,pcdummy/lxd,jsavikko/lxd,stgraber/lxd,georghopp/lxd,stgraber/lxd,erikmack/lxd,Skarlso/lxd,lxc/lxd