check activeQ.Len() before Pop()

[denkensk]

What type of PR is this?

/kind bug
/kind flake

What this PR does / why we need it:

Which issue(s) this PR fixes:

Fixes #

Special notes for your reviewer:

We use activeQ.Pop() to check if the items in activeQ are the same as expected here. If the length of activeQ is less than expected, panic will occur when the pop func is called.

=== RUN   TestPodTimestamp
--- FAIL: TestPodTimestamp (0.30s)
=== RUN   TestPodTimestamp/add_two_pod_to_activeQ_and_sort_them_by_the_timestamp
    --- PASS: TestPodTimestamp/add_two_pod_to_activeQ_and_sort_them_by_the_timestamp (0.10s)
=== RUN   TestPodTimestamp/update_two_pod_to_activeQ_and_sort_them_by_the_timestamp
    --- PASS: TestPodTimestamp/update_two_pod_to_activeQ_and_sort_them_by_the_timestamp (0.10s)
=== RUN   TestPodTimestamp/add_two_pod_to_unschedulableQ_then_move_them_to_activeQ_and_sort_them_by_the_timestamp
    --- FAIL: TestPodTimestamp/add_two_pod_to_unschedulableQ_then_move_them_to_activeQ_and_sort_them_by_the_timestamp (0.10s)
panic: runtime error: index out of range [0] with length 0 [recovered]
	panic: runtime error: index out of range [0] with length 0

Therefore, we need to first check whether the length of activeQ is equal to the expected. If not, it will fail instead of panic.

=== RUN   TestPodTimestamp
--- FAIL: TestPodTimestamp (0.41s)
=== RUN   TestPodTimestamp/add_two_pod_to_activeQ_and_sort_them_by_the_timestamp
    --- PASS: TestPodTimestamp/add_two_pod_to_activeQ_and_sort_them_by_the_timestamp (0.10s)
=== RUN   TestPodTimestamp/update_two_pod_to_activeQ_and_sort_them_by_the_timestamp
    --- PASS: TestPodTimestamp/update_two_pod_to_activeQ_and_sort_them_by_the_timestamp (0.10s)
=== RUN   TestPodTimestamp/add_two_pod_to_unschedulableQ_then_move_them_to_activeQ_and_sort_them_by_the_timestamp
    scheduling_queue_test.go:1526: Expected 3 items to be in activeQ, but got: 2
    --- FAIL: TestPodTimestamp/add_two_pod_to_unschedulableQ_then_move_them_to_activeQ_and_sort_them_by_the_timestamp (0.10s)

=== RUN   TestPodTimestamp/add_one_pod_to_BackoffQ_and_move_it_to_activeQ
    --- PASS: TestPodTimestamp/add_one_pod_to_BackoffQ_and_move_it_to_activeQ (0.10s)

Does this PR introduce a user-facing change?

NONE

Additional documentation e.g., KEPs (Kubernetes Enhancement Proposals), usage docs, etc.:

NONE

[k8s-ci-robot]

@denkensk: This issue is currently awaiting triage.

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[ahg-g]

/lgtm
/approve

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: ahg-g, denkensk

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