Improve wait-for-* execs

Right after start haproxy marks all backends as UP. It marks
problem ones as DOWN only after health-checks. So we should not
rely on BACKEND status while INI is in process.

Change-Id: Ia3743d446826ee1a9d42799a83e14a911a577966
Related-bug: #1391180
(cherry picked from commit 360ef59e8f828243304a669328257be8504b8df6)