If you call the load-iib target you *must* set INDEX_IMAGES, so
let's error out properly if you do not.

Tested as:

        $ unset INDEX_IMAGES
        $ make load-iib
        make -f common/Makefile load-iib
        make[1]: Entering directory '/home/michele/Engineering/cloud-patterns/multicloud-gitops'
        No INDEX_IMAGES defined. Bailing out

        $ export INDEX_IMAGES=foo
        make load-iib
        make -f common/Makefile load-iib
        make[1]: Entering directory '/home/michele/Engineering/cloud-patterns/multicloud-gitops'

        PLAY [IIB CI playbook] ***

Error out from load-iib when INDEX_IMAGES is undefined

…0.25.0

Upgrade vault-helm to v0.25.0

…atic-update