Revert "Make kick triggers consistently use the non-payload version."

This reverts commit 25973f4b5ba797568467632b79e8129ffe007f49. I'm pretty sure
this was not the problem, since I have syncs that *do* work with this
approach.

The problem I'm having with a NOTIFY being ignored is that the database in
question is used in two db groups, once as a source, another as a target. As
it validates, it finds the target record before the source, and stores that
one away. Then the autokick is ignored, because Bucardo thinks the DB is a
target, not a source. Working on a fix for that now.
Listen for autokicks on sources for the sync, not all sources.

I had a database in two dbgroups (and syncs), once as a target and once as a
source. On startup, `validate_sync()` was processing the sync where it was a
target, first, and that was the role saved for it in `$self->{sdb}`. Then,
when `validate_sync()` iterated over `$self->{sdb}`, it thought it was a role,
and so did not have the MCP listen for kicks.

Not only that, but sources from other, previously-validated syncs were
unnecessarily listening for kicks!

So change the code to iterate over the list of DBs for the current call to
`validate_sync()`, not all dbs for all syncs, when figuring out whereq to listen
to for kicks.

Note that the use of the same db object in multiple db groups and syncs *may*
cause issues in other places. It would be smart to audit all code that checks
the value in `{role}` for each hash in `$self->{sdb}` and figure out if it is
appropriate. Since the same db can have different roles in differnt syncs, it
might make sense to record all of its roles and to check all of them, rather
than just rely on the first role found.