Fix locking issues in DB1 HDB backend.

Fix locking issues in DB1 HDB backend.

Multiple concurrent writers would cause the HDB to become corrupted
as the locking was not sufficient to prevent these sorts of issues
from occurring.  We have changed the locking to obtain the appropriate
kind of lock on database open and to hold that lock until the
database closes.  We need to do this as Berkeley DB 1.85 will cache
information from the database in memory and if if this information
is updated without our knowledge then our later writes will corrupt
the database.  We speculate that there would be issues with a single
writer and reader but did not reproduce them.