lib/oe/recipeutils: print just filename in bbappend_recipe() if in temp dir

lib/oe/recipeutils: print just filename in bbappend_recipe() if in temp dir

If you use devtool update-recipe with the --append option, and a "local"
(in oe-local-files) has been modified we copy it into the specified
destination layer. With the way the devtool update-recipe code works now
the source is always a temp directory, and printing paths from within
that is just confusing, so if the path starts with the temp directory
then just print the file name alone.

Signed-off-by: Paul Eggleton <paul.eggleton@linux.intel.com>