mvcc: separate synced/unsynced benchmarks
mvcc: separate synced/unsynced benchmarks

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

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