delete ExpandInputsToCleanCut failure log

Summary:
I decided not even to keep it as an INFO-level log as it is too normal for compactions to be skipped due to locked input files. Removing logging here makes us consistent with how we treat locked files that weren't pulled in due to overlap.

We may want some error handling on line 422, which should never happen when called by `LevelCompactionBuilder::PickCompaction`, as `SetupInitialFiles` skips compactions where overlap causes the output level to pull in locked files.
Closes https://github.com/facebook/rocksdb/pull/2617

Differential Revision: D5458502

Pulled By: ajkr

fbshipit-source-id: c2e5f867c0a77c1812ce4242ab3e085b3eee0bae

db/compaction_picker.cc

@@ -234,11 +234,6 @@ bool CompactionPicker::ExpandInputsToCleanCut(const std::string& cf_name,
   // If, after the expansion, there are files that are already under
   // compaction, then we must drop/cancel this compaction.
   if (AreFilesInCompaction(inputs->files)) {
-    ROCKS_LOG_WARN(
-        ioptions_.info_log,
-        "[%s] ExpandWhileOverlapping() failure because some of the necessary"
-        " compaction input files are currently being compacted.",
-        cf_name.c_str());
     return false;
   }
   return true;