bitbake: command: Fix getCmdLineAction bugs

Executing "bitbake" doesn't get a sane message since the None return value
wasn't being handled correctly. Also fix msg -> cmd_action['msg'] as
otherwise an invalid variable is accessed which then crashes the server
due to the previous bug.

(Bitbake rev: c6211291ae07410832031a5274690437cc2b09a6)

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