fix LDAP Grafana admin logic

Co-authored-by: Adrien Fillon <adrien.fillon@cdiscount.com>
Co-authored-by: Remi Buisson <remi.buisson@cdiscount.com>

pkg/login/ldap.go

@@ -185,7 +185,9 @@ func (a *ldapAuther) GetGrafanaUserFor(ctx *m.ReqContext, ldapUser *LdapUserInfo
 
 		if ldapUser.isMemberOf(group.GroupDN) {
 			extUser.OrgRoles[group.OrgId] = group.OrgRole
-			extUser.IsGrafanaAdmin = group.IsGrafanaAdmin
+			if extUser.IsGrafanaAdmin == nil || *extUser.IsGrafanaAdmin == false {
+				extUser.IsGrafanaAdmin = group.IsGrafanaAdmin
+			}
 		}
 	}