udiskslinuxblockobject: Try issuing BLKRRPART ioctl harder

For some reason even after acquiring a voluntary BSD lock on
the device the BLKRRPART ioctl still fails with EBUSY. Wait
a couple of msec and everything is fine.

So try harder, several attempts, if busy. There might be number
of things going on in the system and it's out of our control
even when holding a lock.

src/udiskslinuxblockobject.c

@@ -1098,23 +1098,31 @@ udisks_linux_block_object_reread_partition_table (UDisksLinuxBlockObject  *objec
     }
   else
     {
-      gint num_tries = 0;
+      gint num_tries;
 
       /* acquire an exclusive BSD lock to prevent udev probes.
        * See also https://systemd.io/BLOCK_DEVICE_LOCKING
        */
+      num_tries = 10;
       while (flock (fd, LOCK_EX | LOCK_NB) != 0)
         {
           g_usleep (100 * 1000); /* microseconds */
-          if (num_tries++ > 5)
+          if (num_tries-- < 0)
             break;
         }
 
-      if (ioctl (fd, BLKRRPART) != 0)
+      num_tries = 5;
+      while (ioctl (fd, BLKRRPART) != 0)
         {
+          if (errno == EBUSY && num_tries-- >= 0)
+            {
+              g_usleep (200 * 1000); /* microseconds */
+              continue;
+            }
           g_set_error (error, G_IO_ERROR, g_io_error_from_errno (errno),
                        "Error re-reading partition table (BLKRRPART ioctl) on %s: %m", device_file);
           ret = FALSE;
+          break;
         }
       close (fd);
     }