Allowed LoadGeneratorFramework to read password from a file.
Allowed LoadGeneratorFramework to read password from a file.

Review: https://reviews.apache.org/r/23695

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