QemuOpts: Convert qemu_opt_set_number() to Error, fix its use

Return the Error object instead of reporting it with
qerror_report_err().

Change callers that assume the function can't fail to pass
&error_abort, so that should the assumption ever break, it'll break
noisily.

Turns out all callers outside its unit test assume that.  We could
drop the Error ** argument, but that would make the interface less
regular, so don't.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
diff --git a/block.c b/block.c
index 9b707e3..f59c4cf 100644
--- a/block.c
+++ b/block.c
@@ -1364,7 +1364,7 @@
 
     opts = qemu_opts_create(bdrv_qcow2.create_opts, NULL, 0,
                             &error_abort);
-    qemu_opt_set_number(opts, BLOCK_OPT_SIZE, total_size);
+    qemu_opt_set_number(opts, BLOCK_OPT_SIZE, total_size, &error_abort);
     ret = bdrv_create(&bdrv_qcow2, tmp_filename, opts, &local_err);
     qemu_opts_del(opts);
     if (ret < 0) {
@@ -5649,7 +5649,7 @@
 
     /* Create parameter list with default values */
     opts = qemu_opts_create(create_opts, NULL, 0, &error_abort);
-    qemu_opt_set_number(opts, BLOCK_OPT_SIZE, img_size);
+    qemu_opt_set_number(opts, BLOCK_OPT_SIZE, img_size, &error_abort);
 
     /* Parse -o options */
     if (options) {
@@ -5731,7 +5731,7 @@
                 goto out;
             }
 
-            qemu_opt_set_number(opts, BLOCK_OPT_SIZE, size);
+            qemu_opt_set_number(opts, BLOCK_OPT_SIZE, size, &error_abort);
 
             bdrv_unref(bs);
         } else {