The important bugfix is to update the last oid when the master verifies a
transaction with new oids.

By resetting the transaction manager at the beginning of the recovery phase,
it become possible to avoid tid/oid holes:
- by reallocating previously unused allocated oids
- when going back "in the past", i.e. reverting to an older version of the
  database (with fewer oids) and/or adjusting the clock