Transaction adds a redo log for each statement. The log is an xrow
header. Some requests don't have a header (local requests), some
do (from remote client, from replication).

When a request had a header, it was written as is to WAL. But
requests from remote client have an xrow header, however barely
filled. Most of its fields are default values, usually 0.
Including group id. Indeed, remote clients should not care about
setting such deep system fields.

That led to a problem when a space had group id local (!= 0), but
it was ignored because in a request header from a remote client
the group id was default (== 0). On the summary, it was possible
to force Tarantool to replicate a replica-local space.

Now group id setting is server-authoritative. Box always sets it
regardless of what is present in an xrow header received from a
client.

Thanks Kostja Osipov (@kostja) for the diagnostics and the
solution.

Closes #4729

(cherry picked from commit 3d0f12968a8f5349eedb1778d6e29950f04785d5)