[PATCH nft] tests: shell: quote reference to array to iterate over empty string

[Pablo Neira Ayuso <pablo@xxxxxxxxxxxxx>]

This patch restores coverage for non-interval set backend.

Use "${FLAGS[@]}" in loop, otherwise empty string is skipped in the
iteration. This snippet:

  FLAGS=("")
  available_flags FLAGS "single"

  for flags in "${FLAGS[@]}" ; do
          echo $flags
  done

... now shows the empty string:

  # bash test.sh

  interval

Fixes: ed927baa4fd8 ("tests: shell: skip pipapo set backend in transactions/30s-stress")
Signed-off-by: Pablo Neira Ayuso <pablo@xxxxxxxxxxxxx>
---
 tests/shell/testcases/transactions/30s-stress | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tests/shell/testcases/transactions/30s-stress b/tests/shell/testcases/transactions/30s-stress
index ef3e1d3e3e4b..e92b922660b8 100755
--- a/tests/shell/testcases/transactions/30s-stress
+++ b/tests/shell/testcases/transactions/30s-stress
@@ -324,7 +324,7 @@ random_elem()
 
 			FLAGS=("")
 			available_flags FLAGS $key
-			for flags in ${FLAGS[@]} ; do
+			for flags in "${FLAGS[@]}" ; do
 				cnt=$((cnt+1))
 				if [ $f -ne fkr ] ;then
 					f=$((f+1))
-- 
2.30.2