bitbake: fetch2/npm: fix broken fetches if more than one npm URL fetched

bitbake: fetch2/npm: fix broken fetches if more than one npm URL fetched

You cannot set a URL-specific value in an object-level variable on
the FetchMethod in urldata_init() or the result is the value specific to
the last URL will be the one that gets set. This prevented fetching more
than one npm:// URL correctly - the other tarballs would not download to
the correct location and do_unpack failed to find them as a result.

Fix required in order to support [YOCTO #9537].

(Bitbake rev: 1435b49ea7d0f9d4cc4a665fb2aa83d1eea7900f)

Signed-off-by: Paul Eggleton <paul.eggleton@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>