Add a unit test to verify compaction filter context

Summary: Add unit tests to make sure CompactionFilterContext::is_manual_compaction_ and CompactionFilterContext::is_full_compaction_ are set correctly.

Test Plan: run the new tests.

Reviewers: haobo, igor, dhruba, yhchiang, ljin

Reviewed By: haobo

CC: nkg-, leveldb

Differential Revision: https://reviews.facebook.net/D17067
Fix DBTest.UniversalCompactionTrigger failure caused by D17067

Summary: D17067 breaks DBTest.UniversalCompactionTrigger because of wrong location of the checking. Fix it.

Test Plan: Run the test and make sure it passes.

Reviewers: igor, haobo

Reviewed By: igor

CC: dhruba, ljin, yhchiang, leveldb

Differential Revision: https://reviews.facebook.net/D17079
Delete rocksdb dir after crashtest

Summary:
We should clean up after ourselves. Last crashtest failed because the disk on the cibuild machine was full.

Also, db_crashtest is supposed to run the test on the same database in every iteration. This isn't the case currently, because every run creates a new tmp directory. It's fixed with this diff.

Test Plan: ran it

Reviewers: ljin

Reviewed By: ljin

CC: leveldb

Differential Revision: https://reviews.facebook.net/D17073
If paranoid_checks -- Mark DB read-only on any IOError

Summary:
Whenever we get an IOError from GetImpl() or NewIterator(), we should immediatelly mark the DB read-only. The same check already exists in Write() and Compaction().

This should help with clients that are somehow missing a file.

Test Plan: make check

Reviewers: dhruba, haobo, sdong, ljin

Reviewed By: dhruba

CC: leveldb

Differential Revision: https://reviews.facebook.net/D17061