Removed unnecessary using directive.
Removed unnecessary using directive.

Review: https://reviews.apache.org/r/36911

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