If you are using SRM to perform its own self validation of 'failover' then VMware encapsulates everything, and so you should not need to anything re NetBackup - because VMware will self discard anything that runs at the alternate DC/site.
If you are failing over for real, and SRM brings up a NetBackup Master Server at an alternate VMware Data Centre then that master server is effectively running live at that DC/site. So, again, I'm don't think there's anything else you need to do.
But - I guess it depends how much of a test you want your SRM test to be?
Maybe you might want to disable all backup policies, and disable all SLPs before failover, so that the master server is quiet. And then after SRM failover, perhaps create (or enable) one test backup policy and perform one backup using a media server and backup storage located at the DR site.
But then maybe all of this config is local to one physical site. You didn't provide much detail.
Maybe all you want to do is restore test whilst running in a failed over state. In which case, again probably best to quiesce / de-activate all backup policies and all SLP policies before SRM failover.
And obviously re-activate when you SRM fail-back to the original VMware DC/site.
