Fixed a bug related to reviewboard_url option in post-reviews.py.
Fixed a bug related to reviewboard_url option in post-reviews.py.

Review: https://reviews.apache.org/r/38870

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