updrade to Longhorn 1.7.2 with allowVolumeCreationWithDegradedAvailability=true

Related issues:

• Closes Upgrade to Longhorn 1.7 (#1901 - closed)
• #1921 (closed) (worked around in this MR, see below)
• #1922 (closed) (not seen in the pipelines of this MR, I tend to think this issue is in fact the same root cause as #1921 (closed))

This MR is:

• renovate MR !3456 (closed)
• ❗ a workaround for issue #1921 (closed) : setting allowVolumeCreationWithDegradedAvailability=true
  • the workaround was proposed by Longhorn developers (see links in the issue)
  • ⚠️ this isn't the safest setting (possible corner case scenarios with dataloss)
  • 👀 the plan is to set it back to allowVolumeCreationWithDegradedAvailability=false as soon as we can use a Longhorn 1.7.3 version where #1921 (closed) is fixed
• debug-on-exit improvement to dump a Longhorn "support bundle"