LU-12777 test: fix to pass facet to facet_fstype

LU-12777 test: fix to pass facet to facet_fstype

Function facet_fstype() expect mgs1 mds1 etc as its
argument, and we used it wrong to pass $mds1 which will
cause following error.

line 1192: lustre-ost1/ost1_FSTYPE: bad substitution

And we fail to detect this is ZFS based OSD, and pool
reimporting will be missed thus failed to mount.

Test-Parameters: trivial clientdistro=el8 testlist=conf-sanity \
                 fstype=zfs envdefinitions=ONLY=103
Test-Parameters: trivial clientdistro=el8 testlist=conf-sanity \
                 fstype=ldiskfs envdefinitions=ONLY=103
Change-Id: Id8fd5b9f17e666614e83e5c1a2399fde8b91b023
Signed-off-by: Wang Shilong <wshilong@ddn.com>
Reviewed-on: https://review.whamcloud.com/36298
Tested-by: jenkins <devops@whamcloud.com>
Reviewed-by: Jian Yu <yujian@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: James Nunez <jnunez@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>