prevent duplicate deploys and make pending deploys easier to spot

treat pending deploys like running deploys -> nobody else can start a deploy,
also giving them more visibility and preventing duplicate deploys when multiple people used to have pendin deploys

@steved555 @pswadi-zendesk @bolddane @jwswj 

### References
 - https://zendesk.atlassian.net/browse/SAMSON-113

### Risks
 - None