ovsdb: Fix mutation of newly inserted rows from Python IDL.

ovsdb: Fix mutation of newly inserted rows from Python IDL.

This patch fixes the scenario, where the mutate operation on a row
is sent in the same transaction as row insert operation. It was
obvserved that this mutate operation was not getting committed
to the OVSDB.

To get around the above problem the "where" condition in an
mutate operation is modified to use the named-uuid to identify
a row created in the current transaction.

Signed-off-by: Amitabha Biswas <abiswas@us.ibm.com>
Suggested-by: Richard Theis <rtheis@us.ibm.com>
Signed-off-by: Ben Pfaff <blp@ovn.org>