rpc: fix memory leak in virNetServerClientNew and virNetServerProgramDispatchCall

rpc: fix memory leak in virNetServerClientNew and virNetServerProgramDispatchCall

In virNetServerProgramDispatchCall, The arg is passed as a void*
and used to point to a certain struct depended on the dispatcher,
so I think it's the memory of the struct's member that leaks and
this memory shuld be freed by xdr_free.

In virNetServerClientNew, client->rx is assigned by invoking
virNetServerClientNew, but isn't freed if client->privateData's
initialization failed, which leads to a memory leak. Thanks to
Liang Peng's suggestion, put virNetMessageFree(client->rx) into
virNetServerClientDispose() to release the memory.

Signed-off-by: jiangjiacheng <jiangjiacheng@huawei.com>
Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
Reviewed-by: Michal Privoznik <mprivozn@redhat.com>