Drop the deprecated and now removed barrier XFS mount options

Both barrier and nobarrier were deprecated with the 4.10 kernel [1] and
then removed [2] with the 4.19 kernel as now used by Fedora >= 28. Both
should be safe to drop at this point.

[1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=4cf4573
[2] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=1c02d50

Change-Id: I6871a7765e3e04122d8d546f43d36bb8415383fc
diff --git a/lib/swift b/lib/swift
index 3b3e608..e2ee0cb 100644
--- a/lib/swift
+++ b/lib/swift
@@ -607,7 +607,7 @@
     # Mount the disk with mount options to make it as efficient as possible
     mkdir -p ${SWIFT_DATA_DIR}/drives/sdb1
     if ! egrep -q ${SWIFT_DATA_DIR}/drives/sdb1 /proc/mounts; then
-        sudo mount -t xfs -o loop,noatime,nodiratime,nobarrier,logbufs=8  \
+        sudo mount -t xfs -o loop,noatime,nodiratime,logbufs=8  \
             ${SWIFT_DISK_IMAGE} ${SWIFT_DATA_DIR}/drives/sdb1
     fi