Fixed minor spacing cleanups in docker containerizer.
Fixed minor spacing cleanups in docker containerizer.

Review: https://reviews.apache.org/r/45453/

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