BlockConf: Call backend functions to detect geometry and blocksizes

geometry: hd_geometry_guess function autodetects the drive geometry.
This patch adds a block backend call, that probes the backing device
geometry. If the inner driver method is implemented and succeeds
(currently only for DASDs), the blkconf_geometry will pass-through
the backing device geometry. Otherwise will fallback to old logic.

blocksize: This patch initializes blocksize properties to 0.
In order to set the property a blkconf_blocksizes was introduced.
If user didn't set physical or logical blocksize, it will
retrieve its value from a driver (only succeeds for DASD), otherwise
it will set default 512 value.

The blkconf_blocksizes call was added to all users of BlkConf.

Signed-off-by: Ekaterina Tumanova <tumanova@linux.vnet.ibm.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-id: 1424087278-49393-6-git-send-email-tumanova@linux.vnet.ibm.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

hw/usb/dev-storage.c

@@ -611,6 +611,7 @@ static void usb_msd_realize_storage(USBDevice *dev, Error **errp)
     }
 
     blkconf_serial(&s->conf, &dev->serial);
+    blkconf_blocksizes(&s->conf);
 
     /*
      * Hack alert: this pretends to be a block device, but it's really