jsonrpc: Use the AsyncoreClient implementation in tests too

No need to have two implementation for the same thing

Change-Id: I6f98075c73000c1a1bea7228eb0590c0678ea900
Signed-off-by: Saggi Mizrahi <smizrahi@redhat.com>
Reviewed-on: http://gerrit.ovirt.org/11625
Reviewed-by: Dan Kenigsberg <danken@redhat.com>
Tested-by: Dan Kenigsberg <danken@redhat.com>