pool: Fix typo that breaks pool.mover.ftp.allow-incoming-connections

Target: trunk
Require-notes: yes
Require-book: no
Request: 2.11
Request: 2.10
Request: 2.9
Request: 2.8
Request: 2.7
Acked-by: Paul Millar <paul.millar@desy.de>
Acked-by: Tigran Mkrtchyan <tigran.mkrtchyan@desy.de>
Patch: https://rb.dcache.org/r/7596/