Fixed the test suite build for Apple clang-600.0.54.
Fixed the test suite build for Apple clang-600.0.54.

Apparently, Apple clang-600.0.54, which is the stock compiler in
10.10.4, does not support passing `{}` as an empty set into a
function.

Review: https://reviews.apache.org/r/49059

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