This adds "set -u" (in addition to the existing -x) to the anchor
scripts. This should fix an issue seen occasionally in the haproxy
chart which is only explainable by the IDENTIFIER variable failing
to get set correctly.
All variables used in the anchor scripts ought to be defined, and
there's no need to rely on blank strings as defaults.
"set -e" was considered for this, but may have unintended side-effects:
-u should be safe and avoid the issue we've seen.
Change-Id: Idbc2f9f77d4754874999d5d83d322a17076c7392