relax constraints on WebsocketRecvStream args
relax constraints on WebsocketRecvStream args

We don't use the Close method any more, so let's make these Writers, not
WriteClosers.

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

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