@renew_failed can cause enormous performance-killing array.

@renew_failed can cause enormous performance-killing array.

The array was populated and values flagged with an accessor, like:
    for (@failedrenews) { $renew_failed[$_] = 1; }
But this means that an array of possibly hundreds of thousands of elements
would have to be auto-populated for high itemnumbers.  A hash is the correct
structure.  We also haven't checked the user input for validity, so we do not know
for sure that @failedrenews really does contain just itemnumbers.

Signed-off-by: Galen Charlton <galen.charlton@liblime.com>