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/tests/test-qemu-opts.c b/tests/test-qemu-opts.c
index 6b0ae33..3fea96a 100644
--- a/tests/test-qemu-opts.c
+++ b/tests/test-qemu-opts.c
@@ -215,10 +215,10 @@
 
 static void test_qemu_opt_get_number(void)
 {
+    Error *err = NULL;
     QemuOptsList *list;
     QemuOpts *opts;
     uint64_t opt;
-    int ret;
 
     list = qemu_find_opts("opts_list_01");
     g_assert(list != NULL);
@@ -238,16 +238,16 @@
     opt = qemu_opt_get_number(opts, "number1", 5);
     g_assert(opt == 5);
 
-    ret = qemu_opt_set_number(opts, "number1", 10);
-    g_assert(ret == 0);
+    qemu_opt_set_number(opts, "number1", 10, &err);
+    g_assert(!err);
 
     /* now we have set number1, should know about it */
     opt = qemu_opt_get_number(opts, "number1", 5);
     g_assert(opt == 10);
 
     /* having reset it, the returned should be the reset one not defval */
-    ret = qemu_opt_set_number(opts, "number1", 15);
-    g_assert(ret == 0);
+    qemu_opt_set_number(opts, "number1", 15, &err);
+    g_assert(!err);
 
     opt = qemu_opt_get_number(opts, "number1", 5);
     g_assert(opt == 15);
@@ -349,10 +349,10 @@
 
 static void test_qemu_opts_reset(void)
 {
+    Error *err = NULL;
     QemuOptsList *list;
     QemuOpts *opts;
     uint64_t opt;
-    int ret;
 
     list = qemu_find_opts("opts_list_01");
     g_assert(list != NULL);
@@ -372,8 +372,8 @@
     opt = qemu_opt_get_number(opts, "number1", 5);
     g_assert(opt == 5);
 
-    ret = qemu_opt_set_number(opts, "number1", 10);
-    g_assert(ret == 0);
+    qemu_opt_set_number(opts, "number1", 10, &err);
+    g_assert(!err);
 
     /* now we have set number1, should know about it */
     opt = qemu_opt_get_number(opts, "number1", 5);