domaininfo: Reload periodically

This patch makes chasquid reload domaininfo periodically, so it notices
any external changes made to it.

It is in line with what we do for aliases and authentication already,
and makes it possible for external removals an additions to the
domaininfo database to be picked up without a restart.

internal/domaininfo/domaininfo.go

@@ -38,11 +38,22 @@ func New(dir string) (*DB, error) {
 	}
 	l.ev = trace.NewEventLog("DomainInfo", dir)
 
+	err = l.Reload()
+	if err != nil {
+		return nil, err
+	}
+
 	return l, nil
 }
 
-// Load the database from disk; should be called once at initialization.
-func (db *DB) Load() error {
+// Reload the database from disk.
+func (db *DB) Reload() error {
+	db.Lock()
+	defer db.Unlock()
+
+	// Clear the map, in case it has data.
+	db.info = map[string]*Domain{}
+
 	ids, err := db.store.ListIDs()
 	if err != nil {
 		return err