Updated C++ style guide to avoid POD const reference in foreach.
Updated C++ style guide to avoid POD const reference in foreach.

Review: https://reviews.apache.org/r/35120

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