Bugfix for tdb transactions

[tridge at samba.org]

Hi Volker,

 > Well, to be honest, I disagree. This changes the rules which
 > locks are to be taken when a recovery is done. A
 > semantically minimal fix would not change this.

A recovery is like a transaction commit as it writes to arbitrary
locations in the file. For a transaction commit we get a write lock on
all records before we do any writes, doing the same thing in recovery
makes sense to me. 

Cheers, Tridge