Trap calls are now executed in LIFO order

[dprotaso]

We tend to add traps at various points in our test scripts. The assumption we have is the trap will be executed when external resources are in a certain state.

ie.

1. Setup Cluster - trap delete_cluster
2. Setup Knative - trap teardown_knative
3. Setup Tests - trap dump_test_failure

Prior traps are executed in FIFO order so the cluster would be torn down before the test dump would occur.

In LIFO order the test dump would occur first, then the teardown of knative and then finally the cluster.

/assign @cardil /assign @upodroid

[knative-prow[bot]]

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[dprotaso]

Actually I think the trap command should be LIFO and that would solve this problem

[dprotaso]

Ok - done please take a look

[krsna-m]

/lgtm