073c5677c7
This is in preparation to switch qemu-server from using '-drive' to the modern '-blockdev' in the QEMU commandline options as well as for the qemu-storage-daemon, which only supports '-blockdev'. The plugins know best what driver and options are needed to access an image, so a dedicated plugin method returning the necessary parameters for '-blockdev' is the most straight-forward. There intentionally is only handling for absolute paths in the default plugin implementation. Any plugin requiring more needs to implement the method itself. With PVE 9 being a major release and most popular plugins not using special protocols like 'rbd://', this seems acceptable. For NBD, etc. qemu-server should construct the blockdev object. Signed-off-by: Fiona Ebner <f.ebner@proxmox.com>