Add synchronized GetLastGTID() method.
Add synchronized GetLastGTID() method.

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