dpkg-native's update-alternatives is broken for offline work so
don't install it.
Also list update-alternatives in the multiprovider whitelist to
avoid unwanted multiple provider warnings when multiple package
backends are enabled.
(From OE-Core rev: 300336fc4a310ed16a14ad041744708d54aae189)
(From OE-Core rev: c90b1faa34e908c7f63e1a64027873858e6d7e8a)
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>