Add a benchmark for MVCCPut.
Add a benchmark for MVCCPut.

BenchmarkMVCCPut10     200000   9489 ns/op    1.05 MB/s
BenchmarkMVCCPut100    200000  10975 ns/op    9.11 MB/s
BenchmarkMVCCPut1000   200000  19402 ns/op   51.54 MB/s
BenchmarkMVCCPut10000   30000  78242 ns/op  127.81 MB/s

While the MB/s does not look good at smaller sizes, we are performing
100k writes per second.

Tweak the MVCCMerge benchmark so that it only performs one merge for
each iteration. This matches up with the expectations of the go
benchmark framework.

SustainFund/cockroach,Kevin-GuanJian/cockroach,Kevin-GuanJian/cockroach,XuWanHong/cockroach-1,maxlang/cockroach,SustainFund/cockroach,veteranlu/cockroach,jamesgraves/cockroach,c4pt0r/cockroach,marcuswestin/cockroach,jess-edwards/cockroach,c4pt0r/cockroach,GokulSrinivas/cockroach,nieyy/cockroach,slavau/cockroach,c4pt0r/cockroach,abhishekgahlot/cockroach,es-chow/cockroach,freakynit/cockroach,bg451/cockroach,sunya123/cockroach,alex/cockroach,hassyma/cockroach,linearb/cockroach,loucash/cockroach,Kevin-GuanJian/cockroach,alunarbeach/cockroach,briceburg/cockroach,ajayaa/cockroach,sunya123/cockroach,jmank88/cockroach,slavau/cockroach,petermattis/cockroach,petermattis/cockroach,hassyma/cockroach,paperstreet/cockroach,jamesgraves/cockroach,c4pt0r/cockroach,cockroachdb/cockroach,linearb/cockroach,freakynit/cockroach,hassyma/cockroach,bg451/cockroach,marcuswestin/cockroach,freakynit/cockroach,yosiat/cockroach,glycerine/cockroach,briceburg/cockroach,es-chow/cockroach,cockroachdb/cockroach,yosiat/cockroach,sunya123/cockroach,fengshao0907/cockroach,yiixiansheng/cockroach,vivekmenezes/cockroach,yananzhi/cockroach,jamesgraves/cockroach,mbertschler/cockroach,jmank88/cockroach,yosiat/cockroach,mbertschler/cockroach,jgautheron/cockroach,cockroachdb/cockroach,marcuswestin/cockroach,arjun4084346/cockroach,abhishekgahlot/cockroach,glycerine/cockroach,jmank88/cockroach,vaibhavarora/cockroach,alex/cockroach,domluna/cockroach,bg451/cockroach,vivekmenezes/cockroach,ngaut/cockroach,jamesgraves/cockroach,freakynit/cockroach,Kevin-GuanJian/cockroach,ngaut/cockroach,freakynit/cockroach,bg451/cockroach,sunya123/cockroach,XuWanHong/cockroach-1,jamesgraves/cockroach,cockroachdb/cockroach,petermattis/cockroach,domluna/cockroach,Kevin-GuanJian/cockroach,mbertschler/cockroach,cuongdo/cockroach,jamesgraves/cockroach,nieyy/cockroach,vaibhavarora/cockroach,yiixiansheng/cockroach,il9ue/cockroach,marcuswestin/cockroach,linearb/cockroach,Abioy/cockroach,il9ue/cockroach,iqstack/cockroach,vaibhavarora/cockroach,mbonaci/cockroach,ajayaa/cockroach,fengshao0907/cockroach,cuongdo/cockroach,paperstreet/cockroach,SustainFund/cockroach,arypurnomoz/cockroach,nieyy/cockroach,fengshao0907/cockroach,jess-edwards/cockroach,jmank88/cockroach,veteranlu/cockroach,veteranlu/cockroach,alunarbeach/cockroach,il9ue/cockroach,cockroachdb/cockroach,vaibhavarora/cockroach,jess-edwards/cockroach,iqstack/cockroach,domluna/cockroach,mbonaci/cockroach,chrisseto/cockroach,Abioy/cockroach,loucash/cockroach,nkhuyu/cockroach,abhishekgahlot/cockroach,vivekmenezes/cockroach,sunya123/cockroach,veteranlu/cockroach,XuWanHong/cockroach-1,maxlang/cockroach,abhishekgahlot/cockroach,petermattis/cockroach,marcuswestin/cockroach,Abioy/cockroach,arjun4084346/cockroach,es-chow/cockroach,cuongdo/cockroach,vaibhavarora/cockroach,cuongdo/cockroach,petermattis/cockroach,mbonaci/cockroach,arjun4084346/cockroach,il9ue/cockroach,hassyma/cockroach,cuongdo/cockroach,fengshao0907/cockroach,yiixiansheng/cockroach,loucash/cockroach,mbonaci/cockroach,sunya123/cockroach,bg451/cockroach,XuWanHong/cockroach-1,XisiHuang/cockroach,mbonaci/cockroach,il9ue/cockroach,XisiHuang/cockroach,arjun4084346/cockroach,jmank88/cockroach,hassyma/cockroach,paperstreet/cockroach,XuWanHong/cockroach-1,yiixiansheng/cockroach,arjun4084346/cockroach,linearb/cockroach,mbertschler/cockroach,nieyy/cockroach,yosiat/cockroach,mbertschler/cockroach,alex/cockroach,slavau/cockroach,linearb/cockroach,iqstack/cockroach,mbonaci/cockroach,veteranlu/cockroach,yiixiansheng/cockroach,alex/cockroach,cuongdo/cockroach,yananzhi/cockroach,alunarbeach/cockroach,chrisseto/cockroach,freakynit/cockroach,ngaut/cockroach,ajayaa/cockroach,iqstack/cockroach,ajayaa/cockroach,cockroachdb/cockroach,briceburg/cockroach,glycerine/cockroach,es-chow/cockroach,fengshao0907/cockroach,vivekmenezes/cockroach,jgautheron/cockroach,paperstreet/cockroach,il9ue/cockroach,vivekmenezes/cockroach,c4pt0r/cockroach,jgautheron/cockroach,GokulSrinivas/cockroach,ajayaa/cockroach,c4pt0r/cockroach,arypurnomoz/cockroach,domluna/cockroach,yosiat/cockroach,nkhuyu/cockroach,alex/cockroach,petermattis/cockroach,Kevin-GuanJian/cockroach,briceburg/cockroach,cockroachdb/cockroach,jess-edwards/cockroach,arypurnomoz/cockroach,jess-edwards/cockroach,nieyy/cockroach,briceburg/cockroach,paperstreet/cockroach,jamesgraves/cockroach,il9ue/cockroach,yananzhi/cockroach,XisiHuang/cockroach,Abioy/cockroach,mbertschler/cockroach,Kevin-GuanJian/cockroach,nkhuyu/cockroach,iqstack/cockroach,alunarbeach/cockroach,SustainFund/cockroach,vaibhavarora/cockroach,vivekmenezes/cockroach,paperstreet/cockroach,XisiHuang/cockroach,GokulSrinivas/cockroach,jess-edwards/cockroach,linearb/cockroach,marcuswestin/cockroach,jgautheron/cockroach,jgautheron/cockroach,SustainFund/cockroach,maxlang/cockroach,maxlang/cockroach,cockroachdb/cockroach,arjun4084346/cockroach,nieyy/cockroach,alunarbeach/cockroach,vivekmenezes/cockroach,ngaut/cockroach,hassyma/cockroach,GokulSrinivas/cockroach,chrisseto/cockroach,loucash/cockroach,il9ue/cockroach,petermattis/cockroach,abhishekgahlot/cockroach,es-chow/cockroach,marcuswestin/cockroach,SustainFund/cockroach,mbertschler/cockroach,slavau/cockroach,jess-edwards/cockroach,paperstreet/cockroach,ajayaa/cockroach,GokulSrinivas/cockroach,petermattis/cockroach,arjun4084346/cockroach,XuWanHong/cockroach-1,arjun4084346/cockroach,iqstack/cockroach,bg451/cockroach,ngaut/cockroach,XuWanHong/cockroach-1,loucash/cockroach,glycerine/cockroach,XisiHuang/cockroach,Abioy/cockroach,chrisseto/cockroach,domluna/cockroach,glycerine/cockroach,chrisseto/cockroach,iqstack/cockroach,abhishekgahlot/cockroach,cuongdo/cockroach,maxlang/cockroach,GokulSrinivas/cockroach,chrisseto/cockroach,nkhuyu/cockroach,nieyy/cockroach,briceburg/cockroach,es-chow/cockroach,yananzhi/cockroach,vivekmenezes/cockroach,domluna/cockroach,arypurnomoz/cockroach,linearb/cockroach,yananzhi/cockroach,marcuswestin/cockroach,sunya123/cockroach,jgautheron/cockroach,yananzhi/cockroach,veteranlu/cockroach,sunya123/cockroach,Abioy/cockroach,maxlang/cockroach,nkhuyu/cockroach,ngaut/cockroach,bg451/cockroach,yosiat/cockroach,nkhuyu/cockroach,paperstreet/cockroach,alex/cockroach,veteranlu/cockroach,es-chow/cockroach,fengshao0907/cockroach,glycerine/cockroach,domluna/cockroach,arypurnomoz/cockroach,jmank88/cockroach,vaibhavarora/cockroach,glycerine/cockroach,arypurnomoz/cockroach,yananzhi/cockroach,slavau/cockroach,slavau/cockroach,nieyy/cockroach,glycerine/cockroach,ngaut/cockroach,vaibhavarora/cockroach,veteranlu/cockroach,XisiHuang/cockroach,cuongdo/cockroach,maxlang/cockroach,maxlang/cockroach,yiixiansheng/cockroach,loucash/cockroach,alunarbeach/cockroach,jmank88/cockroach