Initial commit of CentOS stemcell-builder support.
 * Based on work from https://github.com/pmenglund/bosh/tree/centos
 * Added spec centos_stemcell-vsphere.spec which utilizes new centos stages and existing stages
 * Initializes and builds the chroot root fs using rpm / yum
 * Added a variety of stages named centos_* which implement centos specific implementations of original ubuntu stages
 * CentOS vsphere stem cell can be built by specifying the "CENTOS_ISO" and "base_os=centos" vars in settings.bash.
CentOS - Removed some 'set -x' trace directives from several stages.
Respawn boshagent to satisfy BAT
Remove bosh_agent
changes for bosh_agent
Merge branch 'centos' of github.com:rpetri/bosh