client: parse env variables before sending job-file contents to server

client: parse env variables before sending job-file contents to server

Fixes "fio environment var bug".
https://www.spinics.net/lists/fio/msg07093.html

Add read_ini_data() to parse and expand env variables within job-file
before sending to server. By doing this, clients can control parameters
embedded within the job-file, without server side having to set them
separately.

Reported-by: Jeff Furlong <jeff.furlong@wdc.com>
Signed-off-by: Tomohiro Kusumi <kusumi.tomohiro@gmail.com>
Minor fixups from Jens.

Signed-off-by: Jens Axboe <axboe@kernel.dk>