qemu-option: Replace opt_set() by cleaner opt_validate()
opt_set() frees its argument @value on failure. Slightly unclean;
functions ideally do nothing on failure.
To tidy this up, move opt_create() from opt_set() into its callers,
along with the cleanup. Rename opt_set() to opt_validate(), noting
its similarity to qemu_opts_validate(). Drop redundant parameter
@opts; use opt->opts instead.
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-Id: <
20200707160613.848843-13-armbru@redhat.com>