ovsdb: Correctly implement conditions that include multiple clauses.

ovsdb: Correctly implement conditions that include multiple clauses.

Multiple-clause conditions in OVSDB operations with "where" clauses are
supposed to be conjunctions, that is, the condition is true only if every
clause is true.  In fact, the implementation only checked a single clause
(not necessarily the first one) and ignored the rest.  This fixes the
problem and adds test coverage for multiple-clause conditions.

Reported-by: Shih-Hao Li <shli@nicira.com>