qdev: improve property error reporting.

qdev: improve property error reporting.

Add a error message in case we fail to parse a qdev property.

Also make qemu not abort() in case setting a global property can't be
set.  This used to be a clear programming error.  The introduction of
the -global switch changed that though, so better exit instead (after
printing the new error message).

Signed-off-by: Gerd Hoffmann <[email protected]>
Signed-off-by: Anthony Liguori <[email protected]>