Fix zabbix_agent include_dir creation logic

[AlexPykavy]

SUMMARY

As a string is iterable of chars, the previous logic changed the permissions for all single-character dirs: '/', 'e', 't', 'c', '/', etc.

ISSUE TYPE

• Bugfix Pull Request

COMPONENT NAME

• zabbix_agent role

ADDITIONAL INFORMATION

• IMPORTANT: open terminal session as root because the current version of the role resets the / ownership for all users except root and zabbix group
• run the zabbix_agent role
• check that the ownership of the / is set to root:zabbix and the permissions are smth like drwxr-x---

[AlexPykavy]

Perhaps, it fixes #1365.

[pyrodie18]

OK I think this makes sense. Going to go ahead and pull it in but won't cut the release until #1361 gets updated.