Removed code for old agents when handling status updates.
Removed code for old agents when handling status updates.

0.x agents are no longer supported.

Review: https://reviews.apache.org/r/59218

kaysoky/mesos,abudnik/mesos,dforsyth/mesos,zmalik/mesos,kaysoky/mesos,jpeach/mesos,chhsia0/mesos,abudnik/mesos,jpeach/mesos,gsantovena/mesos,kaysoky/mesos,kaysoky/mesos,Gilbert88/mesos,Gilbert88/mesos,Gilbert88/mesos,reneploetz/mesos,chhsia0/mesos,reneploetz/mesos,zmalik/mesos,jpeach/mesos,asamerh4/mesos,dforsyth/mesos,zmalik/mesos,abudnik/mesos,gsantovena/mesos,verizonlabs/mesos,Gilbert88/mesos,gsantovena/mesos,asamerh4/mesos,kaysoky/mesos,jpeach/mesos,abudnik/mesos,neilconway/mesos,dforsyth/mesos,asamerh4/mesos,chhsia0/mesos,zmalik/mesos,neilconway/mesos,gsantovena/mesos,verizonlabs/mesos,Gilbert88/mesos,verizonlabs/mesos,Gilbert88/mesos,abudnik/mesos,verizonlabs/mesos,verizonlabs/mesos,jpeach/mesos,gsantovena/mesos,asamerh4/mesos,andschwa/mesos,dforsyth/mesos,chhsia0/mesos,dforsyth/mesos,dforsyth/mesos,neilconway/mesos,andschwa/mesos,andschwa/mesos,reneploetz/mesos,abudnik/mesos,kaysoky/mesos,Gilbert88/mesos,dforsyth/mesos,neilconway/mesos,zmalik/mesos,andschwa/mesos,neilconway/mesos,andschwa/mesos,andschwa/mesos,jpeach/mesos,chhsia0/mesos,reneploetz/mesos,abudnik/mesos,reneploetz/mesos,asamerh4/mesos,asamerh4/mesos,gsantovena/mesos,andschwa/mesos,kaysoky/mesos,verizonlabs/mesos,neilconway/mesos,neilconway/mesos,asamerh4/mesos,chhsia0/mesos,zmalik/mesos,reneploetz/mesos,zmalik/mesos,verizonlabs/mesos,reneploetz/mesos,gsantovena/mesos,jpeach/mesos,chhsia0/mesos