Bug 13937: (RM follow-up) Set working directory for daemon mode.

Bug 13937: (RM follow-up) Set working directory for daemon mode.

When running as a daemon under Net::Z3950::SimpleServer YAZ requires a
little help to know where it's "working directory" is located so
relative paths in config files may resolve correctly.

This patch passes the working directory as prescribed on
https://software.indexdata.com/yaz/doc/server.invocation.html such that
the resolution of the cql2rpn filepath works as expected in tests.

Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>