update the mkfs.xfs path
While trying to add centos-7 gate job to swift tests
this script failed calling mkfs.xfs. Updating to use the full path
so that it can be used both on centos and ubuntu
# create a large-ish file that we'll mount as a loopback
truncate -s 1GB {xfs_file}
# format the new file as xfs
- mkfs.xfs {xfs_file}
+ /sbin/mkfs.xfs {xfs_file}
# loopback mount the file
mkdir -p {xfs_mount_point}
sudo mount -o loop,noatime,nodiratime {xfs_file} {xfs_mount_point}
