src/comm.c: Usage of OPENVAS_NVT_DIR instead of include_folders / plugins_folder

[cfi-gb]

Steps to reproduce:

1. Have a fresh trunk / master installation in /opt/openvas and a OPENVAS_NVT_DIR to /opt/openvas/var/lib/openvas/plugins/

2. Point the /opt/openvas/etc/openvassd.conf to the following path:

plugins_folder = /usr/src/nvts/scripts
include_folders = /usr/src/nvts/scripts

3. Start services without running greenbone-nvt-sync

4. Check the /var/log/syslog (not the openvassd.log) and see the following log entry:

Mar  5 15:18:43 localhost openvassd[1506]: grep: /opt/openvas/var/lib/openvas/plugins/plugin_feed_info.inc: No such file or directory

It seems the relevant code line is:

https://github.com/greenbone/openvas-scanner/blob/v5.1.1/src/comm.c#L361

where the fixed OPENVAS_NVT_DIR is used.

[cfi-gb]

Fixed through #28