tests: Load confidential_kbs.sh in k8s-guest-pull-iamge.bats

Some of the tests call set_metadata_annotation() for updating the kernel
parameters. For `kata-qemu-se`, repack_secure_image() is called which is
defined in `lib_se.sh` and sourced by `confidential_kbs.sh`.

This commit ensures that the function call chain for the relevant
`KATA_HYPERVISOR` is properly handled.

Signed-off-by: Hyounggyu Choi <Hyounggyu.Choi@ibm.com>

tests/integration/kubernetes/k8s-guest-pull-image.bats

@@ -7,6 +7,7 @@
 
 load "${BATS_TEST_DIRNAME}/lib.sh"
 load "${BATS_TEST_DIRNAME}/confidential_common.sh"
+load "${BATS_TEST_DIRNAME}/confidential_kbs.sh"
 
 setup() {
     if ! is_confidential_runtime_class; then