Fix variable naming (undefined) in zabbix_web role

[loricvdt]

SUMMARY

Changed variable names in zabbix_web role to resolve undefined error

ISSUE TYPE

• Bugfix Pull Request

COMPONENT NAME

zabbix_web role

ADDITIONAL INFORMATION

Running the role would error out when setting the Debian apt repository fact: zabbix_server_version is undefined.

Fix renames it to zabbix_web_version (like everywhere else in the role) and I took the opportunity to rename zabbix_server_apt_repository to zabbix_web_apt_repository.