Minor doc updates
What does this MR do?
Adds to and clarifies some documentation. Specifically, when using gdb
to debug you need to detach and exit when done. Next, this clarifies the type of file locking that we require.
Thanks to @northrup for the details about mandatory vs. advisory file locking.
Note: These were two really small changes so I combined in to one merge request. However, I left the commits separate for clarity.