[JENKINS-43936] Only migrate legacy users once per restart
[JENKINS-43936] Only migrate legacy users once per restart

(cherry picked from commit f091c9de34e2c8fcaf93966180226dea52f90e38)

DanielWeber/jenkins,bkmeneguello/jenkins,v1v/jenkins,Jochen-A-Fuerbacher/jenkins,Jochen-A-Fuerbacher/jenkins,amuniz/jenkins,kohsuke/hudson,damianszczepanik/jenkins,ErikVerheul/jenkins,DanielWeber/jenkins,rsandell/jenkins,Jimilian/jenkins,amuniz/jenkins,DanielWeber/jenkins,stephenc/jenkins,andresrc/jenkins,pjanouse/jenkins,sathiya-mit/jenkins,pjanouse/jenkins,stephenc/jenkins,patbos/jenkins,jenkinsci/jenkins,aldaris/jenkins,dariver/jenkins,ErikVerheul/jenkins,MarkEWaite/jenkins,recena/jenkins,DanielWeber/jenkins,godfath3r/jenkins,oleg-nenashev/jenkins,bkmeneguello/jenkins,dariver/jenkins,damianszczepanik/jenkins,rsandell/jenkins,kohsuke/hudson,v1v/jenkins,MarkEWaite/jenkins,damianszczepanik/jenkins,viqueen/jenkins,ikedam/jenkins,sathiya-mit/jenkins,escoem/jenkins,rsandell/jenkins,rsandell/jenkins,ikedam/jenkins,damianszczepanik/jenkins,daniel-beck/jenkins,jenkinsci/jenkins,godfath3r/jenkins,aldaris/jenkins,pjanouse/jenkins,viqueen/jenkins,dariver/jenkins,sathiya-mit/jenkins,batmat/jenkins,Jochen-A-Fuerbacher/jenkins,escoem/jenkins,v1v/jenkins,Jimilian/jenkins,patbos/jenkins,kohsuke/hudson,ErikVerheul/jenkins,patbos/jenkins,ErikVerheul/jenkins,daniel-beck/jenkins,Vlatombe/jenkins,amuniz/jenkins,kohsuke/hudson,damianszczepanik/jenkins,aldaris/jenkins,batmat/jenkins,jenkinsci/jenkins,jenkinsci/jenkins,dariver/jenkins,amuniz/jenkins,recena/jenkins,sathiya-mit/jenkins,ErikVerheul/jenkins,oleg-nenashev/jenkins,batmat/jenkins,MarkEWaite/jenkins,jenkinsci/jenkins,sathiya-mit/jenkins,MarkEWaite/jenkins,amuniz/jenkins,oleg-nenashev/jenkins,recena/jenkins,ErikVerheul/jenkins,Vlatombe/jenkins,bkmeneguello/jenkins,bkmeneguello/jenkins,kohsuke/hudson,patbos/jenkins,stephenc/jenkins,daniel-beck/jenkins,andresrc/jenkins,batmat/jenkins,amuniz/jenkins,kohsuke/hudson,daniel-beck/jenkins,bkmeneguello/jenkins,sathiya-mit/jenkins,bkmeneguello/jenkins,pjanouse/jenkins,patbos/jenkins,kohsuke/hudson,Jimilian/jenkins,ikedam/jenkins,Vlatombe/jenkins,MarkEWaite/jenkins,ikedam/jenkins,oleg-nenashev/jenkins,Jimilian/jenkins,batmat/jenkins,Jochen-A-Fuerbacher/jenkins,escoem/jenkins,Jimilian/jenkins,Jochen-A-Fuerbacher/jenkins,DanielWeber/jenkins,Jochen-A-Fuerbacher/jenkins,dariver/jenkins,patbos/jenkins,ikedam/jenkins,Vlatombe/jenkins,godfath3r/jenkins,batmat/jenkins,pjanouse/jenkins,dariver/jenkins,andresrc/jenkins,damianszczepanik/jenkins,viqueen/jenkins,andresrc/jenkins,rsandell/jenkins,v1v/jenkins,v1v/jenkins,andresrc/jenkins,pjanouse/jenkins,jenkinsci/jenkins,rsandell/jenkins,daniel-beck/jenkins,escoem/jenkins,daniel-beck/jenkins,jenkinsci/jenkins,escoem/jenkins,recena/jenkins,MarkEWaite/jenkins,damianszczepanik/jenkins,escoem/jenkins,godfath3r/jenkins,rsandell/jenkins,Jimilian/jenkins,v1v/jenkins,recena/jenkins,rsandell/jenkins,pjanouse/jenkins,ikedam/jenkins,godfath3r/jenkins,godfath3r/jenkins,MarkEWaite/jenkins,stephenc/jenkins,Jochen-A-Fuerbacher/jenkins,godfath3r/jenkins,andresrc/jenkins,patbos/jenkins,aldaris/jenkins,recena/jenkins,Vlatombe/jenkins,recena/jenkins,damianszczepanik/jenkins,stephenc/jenkins,ikedam/jenkins,DanielWeber/jenkins,Vlatombe/jenkins,andresrc/jenkins,stephenc/jenkins,batmat/jenkins,Jimilian/jenkins,jenkinsci/jenkins,aldaris/jenkins,Vlatombe/jenkins,daniel-beck/jenkins,ErikVerheul/jenkins,stephenc/jenkins,ikedam/jenkins,viqueen/jenkins,dariver/jenkins,oleg-nenashev/jenkins,bkmeneguello/jenkins,daniel-beck/jenkins,aldaris/jenkins,oleg-nenashev/jenkins,aldaris/jenkins,escoem/jenkins,DanielWeber/jenkins,v1v/jenkins,viqueen/jenkins,sathiya-mit/jenkins,kohsuke/hudson,oleg-nenashev/jenkins,MarkEWaite/jenkins,viqueen/jenkins,amuniz/jenkins,viqueen/jenkins