lib: test-var-expand - use test_assert_idx() inside loops It helps narrow down which test has failed.
lib: test-var-expand - use test_assert_idx() inside loops
It helps narrow down which test has failed.

Signed-off-by: Phil Carmody <e888d2bd6f13f82caa51a37c03d034c76f661ba3@dovecot.fi>

LTD-Beget/dovecot,LTD-Beget/dovecot,LTD-Beget/dovecot,LTD-Beget/dovecot,LTD-Beget/dovecot