init: T2044: fix "binary operator expected" when two or more RPKI caches are defined

Fix commit 9b8e11e07 ("init: T2044: only start rpki if cache is configured")
which showed a disturbing error on tty0 after boot that a "binary operator
expected" when checking for RPKI caches when multiple results got returned.

(cherry picked from commit a5ac522f8c675ee2b2c2f4f08be7c41943632e94)