Bring back listing LDAP users temporarly (#14760)

In previous releases, mc admin user list would return the list of users
that have policies mapped in IAM database. However, this was removed but
this commit will bring it back until we revamp this.

cmd/iam.go

@@ -694,6 +694,28 @@ func (sys *IAMSys) ListUsers() (map[string]madmin.UserInfo, error) {
 	return sys.store.GetUsers(), nil
 }
 
+// ListLDAPUsers - list LDAP users which has
+func (sys *IAMSys) ListLDAPUsers() (map[string]madmin.UserInfo, error) {
+	if !sys.Initialized() {
+		return nil, errServerNotInitialized
+	}
+
+	if sys.usersSysType != LDAPUsersSysType {
+		return nil, errIAMActionNotAllowed
+	}
+
+	<-sys.configLoaded
+
+	ldapUsers := make(map[string]madmin.UserInfo)
+	for user, policy := range sys.store.GetUsersWithMappedPolicies() {
+		ldapUsers[user] = madmin.UserInfo{
+			PolicyName: policy,
+			Status:     madmin.AccountEnabled,
+		}
+	}
+	return ldapUsers, nil
+}
+
 // IsTempUser - returns if given key is a temporary user.
 func (sys *IAMSys) IsTempUser(name string) (bool, string, error) {
 	if !sys.Initialized() {