[mesh-forwarder] ensure message allocation with correct priority (#7203)
[mesh-forwarder] ensure message allocation with correct priority (#7203)

This commit fixes the incorrect call to `MessagePool::New()` to
allocate a message in `MeshForwarder::HandleMesh()` method. The
existing code calls `New(Message::kType6lowpan, priority)` with two
parameters which maps to the flavor `New()` method with three
parameters with last one (`Message::Settings`) being optional
(having a default value). Basically, the existing code treats the
`priority` (second argument) as `aReserveHeader` parameter in the
`New()` instead of the message priority.
jwhui/openthread,openthread/openthread,jwhui/openthread,abtink/openthread,srickardti/openthread,jwhui/openthread,abtink/openthread,abtink/openthread,srickardti/openthread,abtink/openthread,srickardti/openthread,jwhui/openthread,openthread/openthread,srickardti/openthread,openthread/openthread,openthread/openthread