jsonrpc: Fix race in ProtonReactor and add better delivery semantics

Change-Id: Ie53d6f4b8a119f8a9e366b717c22ba38bcc99e80
Signed-off-by: Saggi Mizrahi <smizrahi@redhat.com>
Reviewed-on: http://gerrit.ovirt.org/10256
Reviewed-by: Adam Litke <agl@us.ibm.com>
Reviewed-by: Dan Kenigsberg <danken@redhat.com>
Tested-by: Dan Kenigsberg <danken@redhat.com>