bitbake: lib: Clean up various file access syntax

bitbake: lib: Clean up various file access syntax

Python 3 is stricter about how files are accessed. Specficially:

 * Use open(), not file()
 * Use binary mode for binary files (when checksumming)
 * Use with statements to ensure files get closed
 * Add missing file close statements

(Bitbake rev: 9f08b901375ba640f47596f1bcf43f98a931550f)

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>