don't set error metadata unless it is explicit
don't set error metadata unless it is explicit

This way we pass the error message directly to the client unless overridden by
the message metadata somehow.

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

georghopp/lxd,pcdummy/lxd,benaryorg/lxd,akshaykarle/lxd,ollie314/lxd,dvbportal/osx-lxd,basvanbeek/lxd,pcdummy/lxd,dustinkirkland/lxd,techtonik/lxd,basvanbeek/lxd,Malizor/lxd,tych0/lxd,basvanbeek/lxd,stgraber/lxd,lxc/lxd,ericsnowcurrently/lxd,atxwebs/lxd,jensg-st/lxd,Skarlso/lxd,mikemccracken/lxd,benaryorg/lxd,rrva/lxd,mjeanson/lxd,beni55/lxd,lxc/lxd,smoser/lxd,Malizor/lxd,hallyn/lxd,erikmack/lxd,stgraber/lxd,stgraber/lxd,lxc/lxd,stgraber/lxd,georghopp/lxd,ericsnowcurrently/lxd,mikemccracken/lxd,rcj4747/lxd,Skarlso/lxd,ollie314/lxd,rcj4747/lxd,akshaykarle/lxd,mjeanson/lxd,yura-pakhuchiy/lxd,chrisglass/lxd,techtonik/lxd,dvbportal/osx-lxd,erikmack/lxd,jsavikko/lxd,achanda/lxd,chrisglass/lxd,erikmack/lxd,jsavikko/lxd,lxc/lxd,rcj4747/lxd,sl1pm4t/lxd,sl1pm4t/lxd,dvbportal/osx-lxd,atxwebs/lxd,mikemccracken/lxd,chrisglass/lxd,atxwebs/lxd,hallyn/lxd,ericsnowcurrently/lxd,beni55/lxd,yura-pakhuchiy/lxd,yura-pakhuchiy/lxd,achanda/lxd,stgraber/lxd,jumpstarter-io/lxd,dustinkirkland/lxd,Skarlso/lxd,stgraber/lxd,lxc/lxd,jumpstarter-io/lxd,lxc/lxd,Skarlso/lxd,hallyn/lxd,smoser/lxd,rrva/lxd,georghopp/lxd,jensg-st/lxd,jumpstarter-io/lxd,jsavikko/lxd,hallyn/lxd,pcdummy/lxd,tych0/lxd,lxc/lxd,sl1pm4t/lxd,achanda/lxd,ollie314/lxd,stgraber/lxd,hallyn/lxd,mjeanson/lxd,hallyn/lxd,smoser/lxd,benaryorg/lxd,beni55/lxd,dustinkirkland/lxd,akshaykarle/lxd,jensg-st/lxd,rrva/lxd,atxwebs/lxd,Malizor/lxd,tych0/lxd,techtonik/lxd