Windows: Changed the shell used by the docker containerizer.
Windows: Changed the shell used by the docker containerizer.

This changes the command given to the Docker CLI when the CommandInfo
specifies `shell=true`.  Instead of `/bin/sh -c`, the Windows command
will be `cmd /c`.

Review: https://reviews.apache.org/r/53716/

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