overlay: rename OVERLAY_LOWER/UPPER/WORK_DIR

As preparation step for configuring test/scratch base fs
for overlay tests:

- Rename OVERLAY_LOWER/UPPER/WORK_DIR => OVL_LOWER/UPPER/WORK
  because we want to use OVL_ prefix for all base fs vars

- Prepend "ovl-" prefix to lower/upper/work path values to
  isolate the overlay test dirs when running on a base fs
  that is also used to run non overlay tests

- Make those vars values non-configurable, because lower/upper/work
  directory names are an internal test detail which should
  not concern the user and because we wish to simplify
  and document the overlay tests setup

- Add helper _filter_ovl_dirs and use it to filter output
  of test overlay/023 which matches the constant string "work"

Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Reviewed-by: Eryu Guan <eguan@redhat.com>
Signed-off-by: Eryu Guan <eguan@redhat.com>

1 files changed, 1 insertions, 1 deletions

diff --git a/tests/overlay/019 b/tests/overlay/019
index 41ce63b8..9177acb3 100755
--- a/tests/overlay/019
+++ b/tests/overlay/019
@@ -51,7 +51,7 @@ _require_scratch
 # Remove all files from previous tests
 _scratch_mkfs
 
-lowerdir=$SCRATCH_DEV/$OVERLAY_LOWER_DIR
+lowerdir=$SCRATCH_DEV/$OVL_LOWER
 mkdir -p $lowerdir
 
 _scratch_mount