OVH doesn't support forking and misbehave when receiving different to tags
on 183 and 200OK.

Use case:

client1 rings first -> sends first 183 ringing
client2 take call -> sends 200OK

OVH then sends an ACK followed by a BYE.
Sending of a BYE to non-established call is bad; moreover the request URI is
wrong.

The workaround consists in removing the "to tag".
The call can be established and paused/resumed.