add dbname_override to java_vtgate_test_helper
add dbname_override to java_vtgate_test_helper

By adding dbname_override flag, it makes caller be able to specify a
different dbname other than the default: vt_ + keyspace

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