Include Run Now Tasks in Concurrent Discovery/Benchmark Task Limit

NetBrain currently applies its concurrent task execution limit, configured under System Management Task Manager, only to Discovery and Benchmark tasks that are scheduled to run. Tasks initiated through Run Now are not counted against this limit, so the total number of simultaneous task executions can exceed the configured maximum when manual runs occur alongside scheduled ones. This enhancement would extend the existing concurrency limit setting to also include Run Now-initiated Discovery and Benchmark tasks, so that the combined count of scheduled and manually triggered executions is constrained by a single configured maximum. This would help administrators, particularly in multi-tenant or multi-domain environments, avoid overloading the NetBrain system and network devices due to unplanned concurrent task execution.