Fixed flaky MasterAuthorizationTest.DuplicateRegistration test.
Fixed flaky MasterAuthorizationTest.DuplicateRegistration test.

Review: https://reviews.apache.org/r/37202

neilconway/mesos,chhsia0/mesos,kaysoky/mesos,yuquanshan/customizedMesos,gsantovena/mesos,neilconway/mesos,craimbert/mesos,gsantovena/mesos,asamerh4/mesos,abudnik/mesos,dforsyth/mesos,gsantovena/mesos,Gilbert88/mesos,neilconway/mesos,chhsia0/mesos,zmalik/mesos,gsantovena/mesos,andschwa/mesos,dforsyth/mesos,Gilbert88/mesos,gsantovena/mesos,zmalik/mesos,zmalik/mesos,reneploetz/mesos,dforsyth/mesos,craimbert/mesos,craimbert/mesos,kaysoky/mesos,andschwa/mesos,chhsia0/mesos,reneploetz/mesos,chhsia0/mesos,abudnik/mesos,Aman-Jain-14/customizedMesos,Aman-Jain-14/customizedMesos,reneploetz/mesos,jpeach/mesos,zmalik/mesos,craimbert/mesos,Aman-Jain-14/customizedMesos,gsantovena/mesos,zmalik/mesos,Gilbert88/mesos,abudnik/mesos,Gilbert88/mesos,yuquanshan/customizedMesos,verizonlabs/mesos,asamerh4/mesos,kaysoky/mesos,craimbert/mesos,neilconway/mesos,zmalik/mesos,jpeach/mesos,abudnik/mesos,yuquanshan/customizedMesos,reneploetz/mesos,dforsyth/mesos,neilconway/mesos,yuquanshan/customizedMesos,dforsyth/mesos,reneploetz/mesos,verizonlabs/mesos,asamerh4/mesos,Aman-Jain-14/customizedMesos,verizonlabs/mesos,Gilbert88/mesos,kaysoky/mesos,chhsia0/mesos,neilconway/mesos,verizonlabs/mesos,andschwa/mesos,yuquanshan/customizedMesos,Gilbert88/mesos,dforsyth/mesos,andschwa/mesos,kaysoky/mesos,reneploetz/mesos,verizonlabs/mesos,asamerh4/mesos,asamerh4/mesos,chhsia0/mesos,jpeach/mesos,andschwa/mesos,jpeach/mesos,Aman-Jain-14/customizedMesos,asamerh4/mesos,verizonlabs/mesos,jpeach/mesos,kaysoky/mesos,abudnik/mesos,jpeach/mesos,yuquanshan/customizedMesos,abudnik/mesos,craimbert/mesos,reneploetz/mesos,gsantovena/mesos,dforsyth/mesos,jpeach/mesos,kaysoky/mesos,verizonlabs/mesos,andschwa/mesos,chhsia0/mesos,neilconway/mesos,andschwa/mesos,zmalik/mesos,Aman-Jain-14/customizedMesos,yuquanshan/customizedMesos,asamerh4/mesos,abudnik/mesos,Gilbert88/mesos,craimbert/mesos,Aman-Jain-14/customizedMesos