Unfortunately expandKeys() notices overlap between the SDK and TARGET
PREFERRED_PROVIDERS entries when we set things up for the SDK recipes.
To avoid this, delete one of the sets of keys to avoid supurious warnings.
(From OE-Core rev: 9068a65baf4a28d04efad9297b16a2883ac42689)
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>