Newer gits return 128 when git config --{rename,remove}-section fails

Newer gits return 128 when git config --{rename,remove}-section fails

As of commit d64ec16c ("git config: reorganize to use parseopt"), git
config --rename-section and --remove-section will now call die()
instead of exit(1) when the section to be renamed or removed doesn't
exist, and die() calls exit(128). So we have to catch exit code 128 as
well.

Signed-off-by: Karl Hasselström <kha@treskal.com>