optimiz commitig compact (#3388)

* optimiz vacuuming volume

* fix bugx

* rename parameters

* fix conflict

* change copyDataBasedOnIndexFile to an instance method

* close needlemap

* optimiz commiting Vacuum volume for  leveldb index

* fix bugs

* fix leveldb loading bugs

* refactor

* fix leveldb loading bug

* add leveldb recovery

* add test case for levelDB

* modify test case to cover all the new branches

* use one tmpNm instead of two instances

* refactor

* refactor

* move setWatermark to the end

* add test for watermark and updating leveldb

* fix error logic

* refactor, add test

* check nil before close needlemapeer
add test case
fix metric bug

* add tests, fix bugs

* adjust log level
remove wrong test case
refactor

* avoid duplicate  updating metric for leveldb index

weed/storage/volume.go

@@ -25,6 +25,7 @@ type Volume struct {
 	Collection         string
 	DataBackend        backend.BackendStorageFile
 	nm                 NeedleMapper
+	tmpNm              TempNeedleMapper
 	needleMapKind      NeedleMapKind
 	noWriteOrDelete    bool // if readonly, either noWriteOrDelete or noWriteCanDelete
 	noWriteCanDelete   bool // if readonly, either noWriteOrDelete or noWriteCanDelete