LPD-69532 Only use listAdminUsers when database will be populated

[anthony-chu]

https://liferay.atlassian.net/browse/LPD-69532

This has been tested in the following cases:

• liferay service not used, no database dumps, empty data directory --> listAdminUsers not called
• liferay service not used, database dump present --> listAdminUsers called
• liferay service not used, data directory not empty --> listAdminUsers called
• liferay service used --> listAdminUsers called