fstests: check: fix unset seqres in run_section()

fstests: check: fix unset seqres in run_section()

While testing, I saw that ".full" is created by _scratch_unmount(), called here:

 725 function run_section()
 ::
 815         if [ ! -z "$SCRATCH_DEV" ]; then
 816           _scratch_unmount 2> /dev/null
 817           # call the overridden mkfs - make sure the FS is built

Ensure seqres is set early in run_section() as a fix.

Signed-off-by: Anand Jain <anand.jain@oracle.com>
Reviewed-by: Zorro Lang <zlang@redhat.com>
Signed-off-by: Zorro Lang <zlang@kernel.org>