Check for running deployment

[janatzend]

A deployment which is being started before another deployment has been finished, can cause an unpredictable behavior in Zend Server. It would be nice to have a flag for the 'deployment' command to check for running deployments before executing the actual deployment. If 'yes', just stop the process (block the deployment)

[slaff]

e57eac2 contains the initial changes for this feature request.
--safe will check if there is on-going deployment and if yes will exit with error
--safe in combination with --wait will play it safe and wait for the on-going to finish before starting the new deployment.

[slaff]

@janatzend Please, check if this is working for you and if yes, close the feature request.