There are two seperate PKGDATA_DIR directories, one for the target and one for
the SDK. Rather than fail when a package can't be found, try the SDK first.
We use a datastore copy to keep the code simple, rather than havng to parameterise
all the packagedata functions.
(From OE-Core rev: 701d8f975c89dc6753188fbcf9d4883650ba5b58)
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>