Need a "drop from queue" button

[gregg-shick]

When selecting a system to use in the CI and the system isn't free, we need to add an opetion to drop yourself out of the queue and free up the slot.

Currently if you select a machine and it is not free, you are in the queue and cannot release yourself regardless if you still want the machine or not. That will cause others to experience delays to gain access to the system.

[arunkoshy]

@gregg-shick we will work on this.