Fixed a bug in slave when launching container.
Fixed a bug in slave when launching container.

Review: https://reviews.apache.org/r/24440

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