QemuOpts: Convert qemu_opt_set_bool() 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/util/qemu-option.c b/util/qemu-option.c
index d3ab65d..4de8326 100644
--- a/util/qemu-option.c
+++ b/util/qemu-option.c
@@ -568,7 +568,8 @@
     opt_set(opts, name, value, false, errp);
 }
 
-int qemu_opt_set_bool(QemuOpts *opts, const char *name, bool val)
+void qemu_opt_set_bool(QemuOpts *opts, const char *name, bool val,
+                       Error **errp)
 {
     QemuOpt *opt;
     const QemuOptDesc *desc = opts->list->desc;
@@ -576,9 +577,9 @@
     opt = g_malloc0(sizeof(*opt));
     opt->desc = find_desc_by_name(desc, name);
     if (!opt->desc && !opts_accepts_any(opts)) {
-        qerror_report(QERR_INVALID_PARAMETER, name);
+        error_set(errp, QERR_INVALID_PARAMETER, name);
         g_free(opt);
-        return -1;
+        return;
     }
 
     opt->name = g_strdup(name);
@@ -586,8 +587,6 @@
     opt->value.boolean = !!val;
     opt->str = g_strdup(val ? "on" : "off");
     QTAILQ_INSERT_TAIL(&opts->head, opt, next);
-
-    return 0;
 }
 
 int qemu_opt_set_number(QemuOpts *opts, const char *name, int64_t val)