The failure is caused by exec $stmt where $stmt has two queries.
mtr with view protocol transforms the first query into a view, leaving
the second query executed in the usual way. mtr being oblivious about
the second query then does not handle its results, resulting in
CR_COMMANDS_OUT_OF_SYNC. We disable view protocol for such edge cases.
After fixing these "Failed to drop view: 0: " further failures emerge
from two of the tests, which are the same problem as MDEV-36454, so we
fix them to by disabling view protocol for the relevant SELECTs.
d27e014e3c