REGTESTS: fix lua-based regtests using tune.lua.smp-preserve-bool

REGTESTS: fix lua-based regtests using tune.lua.smp-preserve-bool

Because of the previous commit, configs making use of lua script without
setting "tune.lua.smp-preserve-bool" explicitly now raise a warning.

However, since 6f746af91 ("REGTESTS: use -dW by default on every
reg-tests"), regtests are not allowed to raise warnings anymore.

Because of this the CI now fails for every tests that relies on Lua.
To fix this, let's explicitly set the "tune.lua.smp-preserve-bool" for
all tests involving Lua. Here we set the value to "on" because we know
it is safe to do so, and this way it will be future-proof.

If ec7443827 ("MINOR: hlua: add option to preserve bool type from smp to
lua") is backported, then this patch must be backported with it (if it
is not trivial to backport, then simply follow this rule: grep for
"lua-load" in reg-tests directory, then for each match, make sure to set
the tune.smp-preserve-bool tunable in the global section.