pings are broken in fixed_irc_server mode

Description of the issue

The iq result is never received by the client.

Relevant debug logs

<7>src/xmpp/xmpp_component.cpp:160:     XMPP RECEIVING: <iq from='louiz@louiz.org/adb3e486-2565-455f-8165-0af14616e215' id='9736712d-36a1-43f2-9f2c-d57ed894bbae-717EB' to='#testicouilles@test.louiz.org/loulou' type='get' xmlns='jabber:component:accept'><ping xmlns='urn:xmpp:ping'/></iq>
<7>src/irc/irc_client.cpp:381:  IRC SENDING: (chat.freenode.net) IrcMessage[PRIVMSG]{loulou}{PING 9736712d-36a1-43f2-9f2c-d57ed894bbae-717EB}
<7>src/irc/irc_client.cpp:343:  IRC RECEIVING: (chat.freenode.net) IrcMessage[PRIVMSG]{loulou}{PING 9736712d-36a1-43f2-9f2c-d57ed894bbae-717EB}(from: loulou!~loulou@2001:bc8:38e7::)
<7>src/xmpp/xmpp_component.cpp:78:      XMPP SENDING: <iq from='loulou%@test.louiz.org' id='BE717-eabb498de75d-c2f9-2f34-1a63-d2176379' to='louiz@louiz.org/adb3e486-2565-455f-8165-0af14616e215' type='get'><ping xmlns='urn:xmpp:ping'/></iq>
<7>src/xmpp/xmpp_component.cpp:160:     XMPP RECEIVING: <iq from='louiz@louiz.org/adb3e486-2565-455f-8165-0af14616e215' id='BE717-eabb498de75d-c2f9-2f34-1a63-d2176379' to='loulou%@test.louiz.org' type='result' xmlns='jabber:component:accept'/>
<7>src/irc/irc_client.cpp:381:  IRC SENDING: (chat.freenode.net) IrcMessage[NOTICE]{loulou%}{PING 9736712d-36a1-43f2-9f2c-d57ed894bbae-717EB}

Notice the loulou%.