Fix CompactRange to apply filter to every key

Summary:
When doing CompactRange(), we should first flush the memtable and then calculate max_level_with_files. Also, we want to compact all the levels that have files, including level `max_level_with_files`.

This patch fixed the unit test.

Test Plan: Added a failing unit test and a fix, so it's not failing anymore.

Reviewers: dhruba, haobo, sdong

Reviewed By: haobo

CC: leveldb, xjin

Differential Revision: https://reviews.facebook.net/D14421

include/rocksdb/db.h

@@ -199,6 +199,7 @@ class DB {
                                    uint64_t* sizes) = 0;
 
   // Compact the underlying storage for the key range [*begin,*end].
+  // The actual compaction interval might be superset of [*begin, *end].
   // In particular, deleted and overwritten versions are discarded,
   // and the data is rearranged to reduce the cost of operations
   // needed to access the data.  This operation should typically only