make DBTest.SharedWriteBuffer to pass MockEnv

Summary: DBTest.SharedWriteBuffer uses an Options that doesn't pass CurrentOptions(), so that it doesn't use MockEnv. However, DBTest's constructor uses MockEnv to call DestoryDB() to clean up, causing uncleaned state before it runs.

Test Plan: Run the test modified to make sure they pass default Env and SharedWriteBuffer now passes MockEnv.

Reviewers: rven, yhchiang, igor

Reviewed By: igor

Subscribers: leveldb, dhruba

Differential Revision: https://reviews.facebook.net/D32475

db/db_test.cc

@@ -3995,7 +3995,7 @@ TEST(DBTest, UniversalCompactionCompressRatio2) {
 }
 
 TEST(DBTest, FailMoreDbPaths) {
-  Options options;
+  Options options = CurrentOptions();
   options.db_paths.emplace_back(dbname_, 10000000);
   options.db_paths.emplace_back(dbname_ + "_2", 1000000);
   options.db_paths.emplace_back(dbname_ + "_3", 1000000);
@@ -4099,7 +4099,7 @@ TEST(DBTest, UniversalCompactionSecondPathRatio) {
 }
 
 TEST(DBTest, LevelCompactionThirdPath) {
-  Options options;
+  Options options = CurrentOptions();
   options.db_paths.emplace_back(dbname_, 500 * 1024);
   options.db_paths.emplace_back(dbname_ + "_2", 4 * 1024 * 1024);
   options.db_paths.emplace_back(dbname_ + "_3", 1024 * 1024 * 1024);
@@ -4212,7 +4212,7 @@ TEST(DBTest, LevelCompactionThirdPath) {
 }
 
 TEST(DBTest, LevelCompactionPathUse) {
-  Options options;
+  Options options = CurrentOptions();
   options.db_paths.emplace_back(dbname_, 500 * 1024);
   options.db_paths.emplace_back(dbname_ + "_2", 4 * 1024 * 1024);
   options.db_paths.emplace_back(dbname_ + "_3", 1024 * 1024 * 1024);
@@ -7154,7 +7154,7 @@ TEST(DBTest, RecoverCheckFileAmount) {
 }
 
 TEST(DBTest, SharedWriteBuffer) {
-  Options options;
+  Options options = CurrentOptions();
   options.db_write_buffer_size = 100000;  // this is the real limit
   options.write_buffer_size    = 500000;  // this is never hit
   CreateAndReopenWithCF({"pikachu", "dobrynia", "nikitich"}, options);