enh(systemd): use /etc/sysconfig/cent* files to get options

[lpinsivy]

Description

Use options defined into /etc/sysconfig directory for centcore and centreontrapd (log file, severity log option, ...)

Type of change

• Patch fixing an issue (non-breaking change)
• New functionality (non-breaking change)
• Breaking change (patch or feature) that might cause side effects breaking part of the Software
• Updating documentation (missing information, typo...)

Target serie

• 2.8.x
• 18.10.x
• 19.04.x (master)

How this pull request can be tested ?

Without this fix:

systemctl status centcore

● centcore.service - Centreon Core
   Loaded: loaded (/usr/lib/systemd/system/centcore.service; disabled; vendor preset: disabled)
   Active: active (running) since mer. 2019-04-03 10:33:21 BST; 1s ago
 Main PID: 5277 (centcore)
   CGroup: /system.slice/centcore.service
           └─5277 /usr/bin/perl /usr/share/centreon/bin/centcore

avril 03 10:33:21 centreon-central-1810 systemd[1]: Started Centreon Core

with the fix:

systemctl status centcore

● centcore.service - Centreon Core
   Loaded: loaded (/usr/lib/systemd/system/centcore.service; disabled; vendor preset: disabled)
   Active: active (running) since mer. 2019-04-03 10:33:57 BST; 5s ago
 Main PID: 5314 (centcore)
   CGroup: /system.slice/centcore.service
           └─5314 /usr/bin/perl /usr/share/centreon/bin/centcore --logfile=/var/log/centreon/centcore.log --severity=error --config=/etc/centreon/conf.pm

avril 03 10:33:57 centreon-central-1810 systemd[1]: Started Centreon Core.

Any relevant details of the configuration to perform the test should be added.

Checklist

Community contributors & Centreon team

• I followed the coding style guidelines provided by Centreon
• I have commented my code, especially new classes, functions or any legacy code modified. (docblock)
• I have commented my code, especially hard-to-understand areas of the PR.
• I have made corresponding changes to the documentation.
• I have rebased my development branch on the base branch (master, maintenance).

Centreon team only

• I have made sure that the unit tests related to the story are successful.
• I have made sure that unit tests covers 80% of the code written for the story.
• I have made sure that acceptance tests related to the story are successful (local and CI)