[BUGFIX] setRespectSysLanguage(FALSE) doesn't prevent language overlay

Solution: When this flag is set to FALSE, do not apply language
overlays.

Resolves: #47192
Releases: 6.0, 6.1, 6.2
Change-Id: Iac0d647fde2f930a63bc6982472b1c76e649601d
Reviewed-on: https://review.typo3.org/21322
Reviewed-by: Georg Ringer
Tested-by: Georg Ringer
Reviewed-by: Paul Dubuc
Tested-by: Paul Dubuc
Reviewed-by: Stanislas Rolland
Tested-by: Stanislas Rolland