recipetool: create: fix falling back to declared license for npm packages
Fix two problems falling back to the "license" field from package.json
when no license file is present:
1) The function that was supposed to return the license field value was
always explicitly returning None, and this was never noticed (because
the test cases never exercised the fallback as they provided license
files for each module).
2) Fix the main package not falling back because it had a default of an
empty list, which evaluates to '' instead of 'Unknown'.
Signed-off-by: Paul Eggleton <paul.eggleton@linux.intel.com> Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
