Fix race in etcdtopo test.
Fix race in etcdtopo test.

The per-node locks weren't being respected everywhere.
Since this is just a fake for tests, I simplified it by requiring
one big lock for all operations.

cloudbearings/vitess,AndyDiamondstein/vitess,kuipertan/vitess,yaoshengzhe/vitess,aaijazi/vitess,yaoshengzhe/vitess,mlc0202/vitess,tirsen/vitess,tjyang/vitess,applift/vitess,ptomasroos/vitess,skyportsystems/vitess,fengshao0907/vitess,vitessio/vitess,dcadevil/vitess,cloudbearings/vitess,cgvarela/vitess,michael-berlin/vitess,dumbunny/vitess,tirsen/vitess,atyenoria/vitess,erzel/vitess,mahak/vitess,kuipertan/vitess,pivanof/vitess,xgwubin/vitess,guokeno0/vitess,HubSpot/vitess,aaijazi/vitess,tirsen/vitess,mapbased/vitess,pivanof/vitess,applift/vitess,atyenoria/vitess,alainjobart/vitess,mahak/vitess,enisoc/vitess,nurblieh/vitess,mahak/vitess,kuipertan/vitess,erzel/vitess,sougou/vitess,guokeno0/vitess,cgvarela/vitess,applift/vitess,dcadevil/vitess,mahak/vitess,kmiku7/vitess-annotated,ptomasroos/vitess,xgwubin/vitess,xgwubin/vitess,fengshao0907/vitess,michael-berlin/vitess,yangzhongj/vitess,tinyspeck/vitess,tirsen/vitess,tirsen/vitess,applift/vitess,erzel/vitess,applift/vitess,applift/vitess,michael-berlin/vitess,kuipertan/vitess,pivanof/vitess,ptomasroos/vitess,fengshao0907/vitess,vitessio/vitess,cloudbearings/vitess,enisoc/vitess,HubSpot/vitess,rnavarro/vitess,guokeno0/vitess,anusornc/vitess,mlc0202/vitess,rnavarro/vitess,michael-berlin/vitess,yangzhongj/vitess,HubSpot/vitess,fengshao0907/vitess,mlc0202/vitess,alainjobart/vitess,cgvarela/vitess,enisoc/vitess,yangzhongj/vitess,kmiku7/vitess-annotated,atyenoria/vitess,dcadevil/vitess,alainjobart/vitess,sougou/vitess,AndyDiamondstein/vitess,kmiku7/vitess-annotated,fengshao0907/vitess,cloudbearings/vitess,tirsen/vitess,rnavarro/vitess,mapbased/vitess,fengshao0907/vitess,dumbunny/vitess,cloudbearings/vitess,erzel/vitess,skyportsystems/vitess,skyportsystems/vitess,mapbased/vitess,kmiku7/vitess-annotated,dumbunny/vitess,dcadevil/vitess,tjyang/vitess,mattharden/vitess,guokeno0/vitess,AndyDiamondstein/vitess,yangzhongj/vitess,kuipertan/vitess,mapbased/vitess,sougou/vitess,enisoc/vitess,dumbunny/vitess,aaijazi/vitess,nurblieh/vitess,anusornc/vitess,atyenoria/vitess,HubSpot/vitess,mahak/vitess,AndyDiamondstein/vitess,tjyang/vitess,kmiku7/vitess-annotated,atyenoria/vitess,tjyang/vitess,guokeno0/vitess,pivanof/vitess,mattharden/vitess,vitessio/vitess,tirsen/vitess,yaoshengzhe/vitess,kmiku7/vitess-annotated,mattharden/vitess,enisoc/vitess,anusornc/vitess,mattharden/vitess,alainjobart/vitess,yaoshengzhe/vitess,cgvarela/vitess,AndyDiamondstein/vitess,sougou/vitess,ptomasroos/vitess,mattharden/vitess,michael-berlin/vitess,mattharden/vitess,atyenoria/vitess,michael-berlin/vitess,skyportsystems/vitess,mattharden/vitess,cgvarela/vitess,nurblieh/vitess,yangzhongj/vitess,mapbased/vitess,kuipertan/vitess,rnavarro/vitess,xgwubin/vitess,alainjobart/vitess,HubSpot/vitess,mlc0202/vitess,mattharden/vitess,mlc0202/vitess,AndyDiamondstein/vitess,dumbunny/vitess,rnavarro/vitess,ptomasroos/vitess,mlc0202/vitess,dcadevil/vitess,vitessio/vitess,HubSpot/vitess,yangzhongj/vitess,enisoc/vitess,skyportsystems/vitess,HubSpot/vitess,tirsen/vitess,kmiku7/vitess-annotated,vitessio/vitess,nurblieh/vitess,mlc0202/vitess,mlc0202/vitess,tirsen/vitess,sougou/vitess,rnavarro/vitess,kuipertan/vitess,cloudbearings/vitess,dumbunny/vitess,xgwubin/vitess,mahak/vitess,tjyang/vitess,vitessio/vitess,fengshao0907/vitess,erzel/vitess,davygeek/vitess,AndyDiamondstein/vitess,guokeno0/vitess,davygeek/vitess,sougou/vitess,mattharden/vitess,ptomasroos/vitess,ptomasroos/vitess,anusornc/vitess,michael-berlin/vitess,tjyang/vitess,michael-berlin/vitess,mlc0202/vitess,AndyDiamondstein/vitess,nurblieh/vitess,nurblieh/vitess,guokeno0/vitess,tinyspeck/vitess,ptomasroos/vitess,fengshao0907/vitess,tinyspeck/vitess,xgwubin/vitess,yaoshengzhe/vitess,tjyang/vitess,davygeek/vitess,dumbunny/vitess,anusornc/vitess,mattharden/vitess,enisoc/vitess,skyportsystems/vitess,applift/vitess,tinyspeck/vitess,mapbased/vitess,mapbased/vitess,guokeno0/vitess,nurblieh/vitess,yangzhongj/vitess,sougou/vitess,rnavarro/vitess,aaijazi/vitess,yangzhongj/vitess,rnavarro/vitess,aaijazi/vitess,atyenoria/vitess,skyportsystems/vitess,pivanof/vitess,pivanof/vitess,yaoshengzhe/vitess,anusornc/vitess,applift/vitess,dumbunny/vitess,pivanof/vitess,erzel/vitess,erzel/vitess,ptomasroos/vitess,vitessio/vitess,sougou/vitess,mahak/vitess,erzel/vitess,aaijazi/vitess,xgwubin/vitess,fengshao0907/vitess,dcadevil/vitess,tjyang/vitess,cgvarela/vitess,pivanof/vitess,xgwubin/vitess,kuipertan/vitess,cgvarela/vitess,kmiku7/vitess-annotated,tinyspeck/vitess,pivanof/vitess,aaijazi/vitess,mapbased/vitess,applift/vitess,alainjobart/vitess,nurblieh/vitess,michael-berlin/vitess,cloudbearings/vitess,tinyspeck/vitess,dumbunny/vitess,mahak/vitess,HubSpot/vitess,atyenoria/vitess,tinyspeck/vitess,skyportsystems/vitess,anusornc/vitess,davygeek/vitess,tjyang/vitess,alainjobart/vitess,erzel/vitess,atyenoria/vitess,davygeek/vitess,davygeek/vitess,yangzhongj/vitess,cloudbearings/vitess,cgvarela/vitess,yaoshengzhe/vitess,rnavarro/vitess,alainjobart/vitess,vitessio/vitess,AndyDiamondstein/vitess,cgvarela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