Update vendored bolt

vendor/github.com/Psiphon-Labs/bolt/db.go

@@ -154,6 +154,15 @@ func (db *DB) String() string {
 func Open(path string, mode os.FileMode, options *Options) (*DB, error) {
 	var db = &DB{opened: true}
 
+	// [Psiphon]
+	// Ensure cleanup on panic so recovery can reset a locked file.
+	defer func() {
+		if r := recover(); r != nil {
+			_ = db.close()
+			panic(r)
+		}
+	}()
+
 	// Set default options if no options are provided.
 	if options == nil {
 		options = DefaultOptions

vendor/vendor.json

@@ -33,10 +33,10 @@
 			"revisionTime": "2017-02-28T16:03:01Z"
 		},
 		{
-			"checksumSHA1": "67iDmaqZg4yqCUDeSlS8uaavYaw=",
+			"checksumSHA1": "v2r1JWhVzxu8q099mzH+VNJ9GiI=",
 			"path": "github.com/Psiphon-Labs/bolt",
-			"revision": "e81ac70c2ed7bcd43e90d848343c42830df1d999",
-			"revisionTime": "2019-07-28T19:25:17Z"
+			"revision": "7494fc3896a47cb6732b87e0b18312cb05ca241a",
+			"revisionTime": "2019-07-30T19:27:05Z"
 		},
 		{
 			"checksumSHA1": "d3DwsdacdFn1/KCG/2uPV1PwR3s=",