embed: fix go 1.7 http issue
embed: fix go 1.7 http issue

go 1.7 introduces HTTP2 compability issue. Now we
need to explicitly enable HTTP2 when TLS is set.

handsomesun/etcd,hongchaodeng/etcd,mkumatag/etcd,coreos/etcd,armstrongli/etcd,etcd-io/etcd,rchicoli/etcd,insequent/etcd,etcd-io/etcd,lorneli/etcd,gyuho/etcd,bdarnell/etcd,qqsun8819/etcd,joshix/etcd,luxas/etcd,dannysauer/etcd,qqsun8819/etcd,sebrandon1/etcd,heyitsanthony/etcd,OyTao/etcd_learning,gyuho/etcd,whuwxl/etcd,glevand/coreos--etcd,akauppi/etcd,mickep76/etcd,sinsharat/etcd,joshix/etcd,endocode/etcd,akauppi/etcd,sebrandon1/etcd,insequent/etcd,rnaveiras/etcd,coreos/etcd,lumjjb/etcd,YuleiXiao/etcd,mqliang/etcd,mkumatag/etcd,OyTao/etcd_learning,yudai/etcd,cockroachdb/etcd,glevand/coreos--etcd,li-ang/etcd,dannysauer/etcd,bluebreezecf/etcd,rnaveiras/etcd,jlamillan/etcd,bdarnell/etcd,YuleiXiao/etcd,visheshnp/etcd,fanminshi/etcd,mqliang/etcd,jlamillan/etcd,plasticbox/etcd,zaphod-concur/etcd,nekto0n/etcd,armstrongli/etcd,endocode/etcd,xiang90/etcd,fanminshi/etcd,tguangch/etcd,ajityagaty/etcd,mqliang/etcd,tguangch/etcd,etcd-io/etcd,mickep76/etcd,vimalk78/etcd,whuwxl/etcd,mkumatag/etcd,luxas/etcd,zaphod-concur/etcd,cockroachdb/etcd,CrazyJvm/etcd,rchicoli/etcd,rnaveiras/etcd,a-robinson/etcd,ajityagaty/etcd,li-ang/etcd,lorneli/etcd,ravigadde/etcd,sinsharat/etcd,vimalk78/etcd,xiang90/etcd,a-robinson/etcd,handsomesun/etcd,yudai/etcd,plasticbox/etcd,ajityagaty/etcd,heyitsanthony/etcd,ravigadde/etcd,hongchaodeng/etcd,nekto0n/etcd,visheshnp/etcd,bluebreezecf/etcd,CrazyJvm/etcd,lumjjb/etcd