utils.py: added sh_quote() function
This function is a wrapper around "shlex.quote()" and can be used in
"${@...}" context where shlex (or pipes, which provides similar
functionality) is unavailable.
Signed-off-by: Enrico Scholz <enrico.scholz@sigma-chemnitz.de>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>