More porting from rep (#2388)

* More porting from rep

* Address review feedback

builtin/logical/postgresql/backend.go

@@ -34,6 +34,8 @@ func Backend(conf *logical.BackendConfig) *backend {
 		},
 
 		Clean: b.ResetDB,
+
+		Invalidate: b.invalidate,
 	}
 
 	b.logger = conf.Logger
@@ -126,6 +128,13 @@ func (b *backend) ResetDB() {
 	b.db = nil
 }
 
+func (b *backend) invalidate(key string) {
+	switch key {
+	case "config/connection":
+		b.ResetDB()
+	}
+}
+
 // Lease returns the lease information
 func (b *backend) Lease(s logical.Storage) (*configLease, error) {
 	entry, err := s.Get("config/lease")