The original code (since 00e6a16d) was assuming aborting the
transaction in autovacuum launcher was sufficient to release all
resources, but in reality the launcher runs quite a lot of code out of
any transactions.  Re-introduce individual cleanup calls to make abort
more robust.

Reported-by: Robert Haas
Discussion: https://postgr.es/m/CA+TgmobQVbz4K_+RSmiM9HeRKpy3vS5xnbkL95gSEnWijzprKQ@mail.gmail.com