dep: fix badger version

revert to v1.6

go.mod

@@ -24,7 +24,7 @@ require (
 	github.com/ipfs/go-cidutil v0.0.2
 	github.com/ipfs/go-datastore v0.0.5
 	github.com/ipfs/go-detect-race v0.0.1
-	github.com/ipfs/go-ds-badger v0.0.4
+	github.com/ipfs/go-ds-badger v0.0.5
 	github.com/ipfs/go-ds-flatfs v0.0.2
 	github.com/ipfs/go-ds-leveldb v0.0.2
 	github.com/ipfs/go-ds-measure v0.0.1
@@ -109,7 +109,9 @@ require (
 	go.uber.org/goleak v0.10.0 // indirect
 	go.uber.org/multierr v1.1.0 // indirect
 	go4.org v0.0.0-20190313082347-94abd6928b1d // indirect
-	golang.org/x/sys v0.0.0-20190610200419-93c9922d18ae
+	golang.org/x/sync v0.0.0-20190423024810-112230192c58 // indirect
+	golang.org/x/sys v0.0.0-20190626221950-04f50cda93cb
+	google.golang.org/appengine v1.4.0 // indirect
 	gopkg.in/cheggaaa/pb.v1 v1.0.28
 	gotest.tools/gotestsum v0.3.4
 )