Add a proper function to process a process-exist control in the daemon.

Add a proper function to process a process-exist control in the daemon.

This controls is only used by samba when samba wants to check if a subrecord held by a <node-id>:<smbd-pid> is still valid or if it can be reclaimed.

If the node is banned or stopped, we kill the smbd process and return that the process does not exist to the caller. This allows us to recover subrecords from stopped/banned nodes where smbd is hung waiting for the databases to thaw.

bz58185