liblinphone: Drop gr parameter of conference information URIs when starting up the

    core in order to keep the backward compatibility.

    The SDK now stores the addresses of the conference without the gr
    parameter as it will negatively affect the high availability capability
    of a server and it will make it dependent on keeping the same gr all the
    time. Therefore clients might be lead to call the conference without
    specifying the gr parameter in the To field of the INVITE.
    If a conference address was stored with the gr parameter, the core would
    not be able to find it as it compares strings and not Address objects

liblinphone @ b570484b

-Subproject commit 69888bc633281fcda9ffc32f79067753e9b78e67
+Subproject commit b570484b8aa3b434c90f453741d9e5483a608eca