[cm] Fix validation for numbered handle

We currently gate checks for numbered_handles in CML on API level HEAD,
which is in-tree only. This introduces strange compatibility issues in
CTF tests that are built at stable API levels, causing those tests to
fail because validation is looking for a field (target_path) that is
omitted when numbered_handles are set.

This change ensures that all locations validating UseProtocol use the
appropriate API level.

Change-Id: Ia9a656e624e74e5efc4052f57d01b83646725ab8
Reviewed-on: https://fuchsia-review.googlesource.com/c/fuchsia/+/1612008
Reviewed-by: Gary Bressler <geb@google.com>
Fuchsia-Auto-Submit: Christopher Johnson <crjohns@google.com>
Commit-Queue: Christopher Johnson <crjohns@google.com>
(cherry picked from commit b22a6a7994b3e8b73e06f579a5fc6167eb71fc59)
Reviewed-on: https://fuchsia-review.googlesource.com/c/fuchsia/+/1617548
Reviewed-by: Sean Lin <shengchanglin@google.com>