apply.sh prematurely declares victory

We've seen various occurrences in the past where:

• the user runs apply.sh
• at the end sylvactl watch ... is run, on sylva-units-status Kustomization
• ... but sylvactl watch sees the target sylva-units-status Kustomization as ready and concludes "All Done!" before anything actually happened

This is a pain for users, but also in CI, where our "upgrade" pipelines are artificially successful (the job terminates too early on "All Done!" despite having in fact not observed anything).

This is not a problem that we fully claim to master yet, but there are a few cases that we understand.

This issue is meant as an umbrella to capture this defect.

/cc @feleouet