dm vdo permassert: audit all of ASSERT to test for VDO_SUCCESS

Also rename ASSERT to VDO_ASSERT and ASSERT_LOG_ONLY to
VDO_ASSERT_LOG_ONLY.

But re-introduce ASSERT and ASSERT_LOG_ONLY as a placeholder
for the benefit of dm-vdo/indexer.

Signed-off-by: Mike Snitzer <snitzer@kernel.org>
Signed-off-by: Matthew Sakai <msakai@redhat.com>