Since the Linux system abort booting when it fails to mount fstab entries,
user may not able to see an error message when we use fstab to mount
/var/lib/scylla on AMI.
Instead of abort booting, we can just abort to start scylla-server.service
when RAID volume is not mounted, using RequiresMountsFor directive of systemd
unit file.
See #3640
Signed-off-by: Takuya ASADA <syuu@scylladb.com>
Message-Id: <20180824185511.17557-1-syuu@scylladb.com>
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