Inconsistent DELAY handling causes "sleep: missing operand" in cc invoke/query flows

While running the test network (e.g. `./network.sh cc invoke` or `cc query`), I hit this error:

sleep: missing operand

After tracing it, this comes from `test-network/scripts/ccutils.sh` where retry loops use:

sleep $DELAY

In some cases, `DELAY` isn’t set, so the command ends up being just `sleep`, which fails.
there is already a `CLI_DELAY` (default = 3), but it isn’t used here.

A simple fix would be to fall back to it, for example:

sleep ${DELAY:-$CLI_DELAY}

this avoids the error and keeps the existing behavior when `DELAY` is provided