qemu-options: Allow -no-user-config again

qemu-options: Allow -no-user-config again

After 1217d6ca2bf28c0febe1bd7d5b3fa912bbf6af2a we error out
explicitly if an unknown -option was passed on the command line.
However, we are doing two pass command line option parsing. In
the first pass we just look for -no-user-config or -nodefconfig
being present which determines whether we load user config or
not. Then in the second pass we finally parse everything else
throwing an error if an unsupported -option was found. Problem is
that in the second pass -no-user-config and -nodefconfig are not
handled explicitly which makes us throw the unsupported option
error.

Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>