fabrics: Add support for volatile configuration

fabrics: Add support for volatile configuration

The fabric resources are global resources and as such should only
modified by one component. So far nvme-cli was the only component
managing connections. With the introduction of nvme-stas we need to
coordinate the access to these resources.

Introduce access coordination feature which allows the external software
to drop volatile configurations files into the /var/nvme directory.

When nvme-cli ls executed(e.g. via the udev rules), the execution
context is evaluated and only resources which belong the application are
considered.

Signed-off-by: Daniel Wagner <dwagner@suse.de>