monitor: move init global earlier

Before this patch, monitor fd helpers might be called even earlier than
monitor_init_globals().  This can be problematic.

After previous work, now monitor_init_globals() does not depend on
accelerator initialization any more.  Call it earlier (before CLI
parsing; that's where the monitor APIs might be called) to make sure it
is called before any of the monitor APIs.

Suggested-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Peter Xu <peterx@redhat.com>
Message-Id: <20180608035511.7439-7-peterx@redhat.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>