sysutils/bareos-server: Disable -Werror flag in traymonitor

When -DNDEBUG is defined -Werror needs to be disabled otherwise
(leaf) port won't build

This is the same fix as for client leaf port
Commit: 15fd15478b93d0264ea9bd8af4acff12c2dbde95

PR: 266721
Reviewed by: antoine (via exp-run)
Approved by: portmgr (blanket, build fix)