The current callers of ovsdb_log_open() always want to lock the file if
they are accessing it for read/write access. An upcoming commit will add
a new caller that does not fit this model (it wants to lock the file
across a wider region) and so the caller should be able to choose whether
to do locking. This commit adds that ability.
Also, get rid of the use of <fcntl.h> flags to choose the open mode, which
has always seemed somewhat crude and which this change would make even
cruder.
An upcoming commit will add support for replicating tables across JSON-RPC
connection. As a prerequisite ovsdb itself must support basic replication.
This commit adds that support and then reimplements the ovsdb file storage
in terms of that replication.
