Fix galera.galera_suspend_slave on FreeBSD
Fix galera.galera_suspend_slave on FreeBSD

Use symbolic signal names (e.g. SIGSTOP) instead of numeric ones (e.g.
19) because the latter are not portable.

natsys/mariadb_10.2,natsys/mariadb_10.2,natsys/mariadb_10.2,natsys/mariadb_10.2,natsys/mariadb_10.2,natsys/mariadb_10.2,natsys/mariadb_10.2,natsys/mariadb_10.2,natsys/mariadb_10.2,natsys/mariadb_10.2,natsys/mariadb_10.2