Compaction always needs to be removed from level0_compactions_in_progress_ for universal compaction

Summary: We always put compaction to level0_compactions_in_progress_ for universal compaction, so we should also remove it. The bug causes assert failure when running manual compaction.

Test Plan:
TEST_TMPDIR=/dev/shm/ ./db_bench --benchmarks=fillrandom,compact --subcompactions=16 --compaction_style=1
always fails on my host. After the fix, it doesn't fail any more.

Reviewers: IslamAbdelRahman, andrewkr, kradhakrishnan, yhchiang

Reviewed By: yhchiang

Subscribers: leveldb, dhruba

Differential Revision: https://reviews.facebook.net/D55017

db/compaction_picker.cc

@@ -141,7 +141,8 @@ CompactionPicker::~CompactionPicker() {}
 
 // Delete this compaction from the list of running compactions.
 void CompactionPicker::ReleaseCompactionFiles(Compaction* c, Status status) {
-  if (c->start_level() == 0) {
+  if (c->start_level() == 0 ||
+      ioptions_.compaction_style == kCompactionStyleUniversal) {
     level0_compactions_in_progress_.erase(c);
   }
   if (!status.ok()) {