virt-make-fs: Round disk size to integer, fix for qemu-img 0.14.

qemu-img used to allow you to specify a fractional image size in bytes
(or at least, it used to ignore the part after the decimal place).  In
qemu-img 0.14 it no longer does this so we round down the size to a
whole number of bytes.

tools/virt-make-fs

@@ -393,6 +393,8 @@ if (!defined $size) {
     }
 }
 
+$size = int ($size);
+
 # Create the output disk.
 # Take the unusual step of invoking qemu-img here.