update idxDelete unit test to fail if it takes too long
update idxDelete unit test to fail if it takes too long

- the main purpose of this is to ensure that deletes of nodes with
a large number of children dont take too long. So the unit test
has been updated to fail if the operation takes more then 10seconds.

raintank/raintank-metric,replay/metrictank,raintank/metrictank,raintank/raintank-metric,raintank/raintank-metric,raintank/metrictank,raintank/metrictank,replay/metrictank,raintank/metrictank,replay/metrictank,replay/metrictank