license: fix LICENSE_CREATE_PACKAGE to stay disabled by default

* as reported by Enrico on #oe
  11:06:50 < ensc|w> JaMa: might this be caused by dc78ef91a2bf01efb8028c9afbe69e506e016265
  which checks for 'd.getVar('LICENSE_CREATE_PACKAGE', True)' evaluating to 'True' for every
  string (including the default 0)

Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>