Refactor Future to use synchronized.
Refactor Future to use synchronized.

Review: https://reviews.apache.org/r/32358

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