Dear maintainers,

The zabbix-web-service.service unit shipped in this package contains the
following directives:

Environment="DAEMON_ARGS= -c /etc/zabbix/zabbix_web_service.conf"
EnvironmentFile=-/etc/default/%p
ExecStart=/usr/sbin/zabbix_web_service -c $DAEMON_ARGS

Both the default 'DAEMON_ARGS' variable and the 'ExecStart' directive
include a '-c' option. If no '/etc/default/zabbix-web-service' exists (the
default) or didn't set 'DAEMON_ARGS', the final command line will contain
two '-c', causing the service to fail, with error:

 ERROR: cannot open configuration file: open -c: no such file or directory

E.g., zabbix_web_service(8) being instructed to read a configuration file
named '-c'.

Please remove the redundant option from 'ExecStart'.