tests: Fix bug in "ovsdb-tool compact" test.

tests: Fix bug in "ovsdb-tool compact" test.

This test examines the OVSDB database log and checks that it contains what
it should for specified transactions.  However, the database log ordering
differs between big-endian and little-endian architectures because it is
written out in hash order.  We don't want to incur the expense of always
sorting the log as we write it out, so instead this commit fixes the
problem by sorting the log as it reads it, using the "test-json" program.