Makefile: clean up "gopath.proto"
Makefile: clean up "gopath.proto"

Signed-off-by: Gyuho Lee <3454051ee3341eb69bdf6fca40899cdad4d86496@gmail.com>

ajityagaty/etcd,cockroachdb/etcd,li-ang/etcd,coreos/etcd,etcd-io/etcd,bdarnell/etcd,sebrandon1/etcd,joshix/etcd,rnaveiras/etcd,rnaveiras/etcd,rnaveiras/etcd,coreos/etcd,sinsharat/etcd,glevand/coreos--etcd,lorneli/etcd,li-ang/etcd,cockroachdb/etcd,vimalk78/etcd,sinsharat/etcd,mkumatag/etcd,mqliang/etcd,joshix/etcd,glevand/coreos--etcd,sebrandon1/etcd,gyuho/etcd,ajityagaty/etcd,mkumatag/etcd,mqliang/etcd,vimalk78/etcd,dannysauer/etcd,bdarnell/etcd,lorneli/etcd,etcd-io/etcd,xiang90/etcd,dannysauer/etcd,xiang90/etcd,mkumatag/etcd,fanminshi/etcd,gyuho/etcd,fanminshi/etcd,ajityagaty/etcd,etcd-io/etcd,mqliang/etcd