Check the Apache multi process model (mpm) in the provided config files

[bschmalhofer]

Every now and then there are problems running OTOBO under Apache. Often this is because the MPM is mpm_event or mpm_worker instead of mpm_prefork. These cases could be detected by requiring mpm_prefork when mod_perl is used. The check can propably be done with a directive.

[bschmalhofer]

Tested the changes with mpm_prefork enabled.
TODO:

• test with mpm_event enabled
• test with mpm_worker enabled

[bschmalhofer]

Here are the tests. Initiially mpm_prefork in enabled. Errors are inspected with systemctl status apache2.service

i. a2dismod mpm_prefork

Jan 19 15:37:02 bernhard-HP-250-G6-Notebook-PC systemd[1]: Starting The Apache HTTP Server...
Jan 19 15:37:02 bernhard-HP-250-G6-Notebook-PC apachectl[6446]: AH00534: apache2: Configuration error: No MPM loade>
Jan 19 15:37:02 bernhard-HP-250-G6-Notebook-PC apachectl[6424]: Action 'start' failed.
Jan 19 15:37:02 bernhard-HP-250-G6-Notebook-PC apachectl[6424]: The Apache error log may have more information.

2. a2enmod mpm_worker

Jan 19 15:40:03 bernhard-HP-250-G6-Notebook-PC systemd[1]: Starting The Apache HTTP Server...
Jan 19 15:40:03 bernhard-HP-250-G6-Notebook-PC apachectl[6645]: AH00526: Syntax error on line 22 of /etc/apache2/si>
Jan 19 15:40:03 bernhard-HP-250-G6-Notebook-PC apachectl[6645]: The Multi-Processing Module mpm_worker is active bu>
Jan 19 15:40:03 bernhard-HP-250-G6-Notebook-PC apachectl[6626]: Action 'start' failed.
Jan 19 15:40:03 bernhard-HP-250-G6-Notebook-PC apachectl[6626]: The Apache error log may have more information.

3. a2dismod mpm_worker && a2enmod mpm_event

Jan 19 15:42:58 bernhard-HP-250-G6-Notebook-PC systemd[1]: Starting The Apache HTTP Server...
Jan 19 15:42:58 bernhard-HP-250-G6-Notebook-PC apachectl[6853]: AH00526: Syntax error on line 18 of /etc/apache2/si>
Jan 19 15:42:58 bernhard-HP-250-G6-Notebook-PC apachectl[6853]: The Multi-Processing Module mpm_event is active but>
Jan 19 15:42:58 bernhard-HP-250-G6-Notebook-PC apachectl[6837]: Action 'start' failed.
Jan 19 15:42:58 bernhard-HP-250-G6-Notebook-PC apachectl[6837]: The Apache error log may have more information.

4. a2dismod mpm_event && a2enmod mpm_prefork
   Webserver looks fine again.