stream: Don't crash when node permission is denied

stream: Don't crash when node permission is denied

The image streaming block job restricts shared permissions of the nodes
it accesses. This can obviously fail when other users already got these
permissions. &error_abort is therefore wrong and can crash. Handle these
errors gracefully and just fail starting the block job.

Reported-by: Nini Gu <[email protected]>
Signed-off-by: Kevin Wolf <[email protected]>
Message-Id: <20210309173451[email protected]>
Reviewed-by: Eric Blake <[email protected]>
Reviewed-by: Alberto Garcia <[email protected]>
Signed-off-by: Kevin Wolf <[email protected]>