Default web_config_owner/group correctly
Default web_config_owner/group correctly

When apache hasn't been evaluated `getvar('::apache::user')` should
return `undef`.

This commit attempts to address 2 issues.

1) In puppet 4 `''` (empty string) != `undef`
2) In stdlib < 4.13.0 instead of `undef`, `getvar('::apache::user')`
returns a literal string `'class ::apache has not been evaluated'`. This
is a bug that was fixed, but it's not too hard to work around.

SoftcomInc/puppet-zabbix,bastelfreak/puppet-zabbix,SoftcomInc/puppet-zabbix,tux-o-matic/puppet-zabbix,bastelfreak/puppet-zabbix,voxpupuli/puppet-zabbix,voxpupuli/puppet-zabbix,tux-o-matic/puppet-zabbix,SoftcomInc/puppet-zabbix,tux-o-matic/puppet-zabbix,voxpupuli/puppet-zabbix,bastelfreak/puppet-zabbix