Make filename handling independent of locale settings

I previously raised this as a bug in TSM with PMR 60127,040,678 but was instructed to raise it with RFE community instead, so here it goes.

The spectrum protect client does not back up all valid files when the locale settings are set to a multibyte locale (such as UTF-8). On a machine with filenames in mixed character sets, backups of any file with a name that is not a valid UTF-8 string fail if the locale of the dsmc process is UTF-8.

This is documented in the BA manual here:
https://www.ibm.com/support/knowledgecenter/en/SSGSG7_7.1.1/com.ibm.itsm.client.doc/c_cfg_nlsupportunix.html

This behaviour is wrong. Filenames are not strings, but byte sequences. Any byte sequence is a valid filename, regardless of system locale. stat() and open() behave the same regardless of the LANG setting.

The problem can be recreated easily on any machine with something like the following (using bash/sh shell and python):
---
cd `mktemp -d`
export LANG='en_US.UTF-8'
cat <<EOF >create_iso88591.py
#!/usr/bin/env python2
name = '\xC6'
with open(name, 'w') as f:
f.write('test')
EOF
python2 create_iso88591.py
ls -l
sudo dsmc incr '*'
---

If the above snippet is run, the created file will not be successfully backed up by dsmc. An error will be printed to the terminal.

Most new machine deployments have UTF-8 locales by default, yet it is very common to have files in mixed character sets due to legacy issues, and even multiple programs with different locale settings running on the same machine. In the current situation, IBM-provided init scripts need to be modified locally by the system administrator to run in a single-byte locale to successfully back up such systems. This is a heavy maintenance burden with a lot of nodes, especially since these changes need to be verified and possibly re-applied on every client update. Furthermore, it means that it is impossible to get terminal and log output in UTF-8 for these machines, which would be desireable.

From my local testing, it does not appear that the BA client does any transcoding of filenames when restoring from a different locale, so there is no obvious reason why filenames would be parsed as strings in this case.

Please change the filename handling in BA client so it can back up any file on the filesystem regardless of filename and locale settings.