LU-12214 selinux: Remove concatenating of selinux context

LU-12214 selinux: Remove concatenating of selinux context

Remove concatenating of context for the temporary mount point
if selinux is enabled.
mount.zfs don't have that option, so revert it for consistency.
It can be added with -o option if needed.

Cray-bug-id: LUS-5992
Test-Parameters: clientselinux mdtcount=4 testlist=sanity,recovery-small,sanity-sec,sanity-selinux

Change-Id: If471de13e201c5cdcb28631b90b2efa13d8f2b4f
Signed-off-by: Alexey Lyashkov <c17817@cray.com>
Reviewed-on: https://review.whamcloud.com/36423
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Sebastien Buisson <sbuisson@ddn.com>
Reviewed-by: Shaun Tancheff <shaun.tancheff@hpe.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>