Passing QDBusUnixFileDescriptor over peer-to-peer connections does not work

Passing QDBusUnixFileDescriptor over peer-to-peer connections does not work. This is for two reasons:

QDBusConnectionPrivate::setPeer does not set this->capabilities, unlike QDBusConnectionPrivate::setConnection which is executed for bus connections, which contains the line:

capabilities = connectionCapabilies(connection);

When this line is added to QDBusConnectionPrivate::setPeer, the second issue is that QDBusConnectionPrivate::setPeer  is called before the authentication is finished, and therefore dbus_connection_can_send_type will always return 0. The solution is probably to wait in QDBusConnectionManager::executeConnectionRequest and qDBusNewConnection until the authentication is done (this is already done for bus connections implicitly by calling dbus_bus_register.

I've attached a patch which should fix this issue.