feat(driver): Add command line flags for using an existing job reservation and to select a host to provision
feat(driver): Add command line flags for using an existing job reservation and to select a host to provision

The flag '--g5k-use-job-reservation' take an existing Job ID, and skip the job reservation part.
The flag '--g5k-only-provision-host' take an hostname an will provision this host, skipping the deployment part.

gfieni/docker-machine-driver-g5k