jsonrpc: Make jsonrpc test timeout constant

Change-Id: Ica0e37cc70b218d2aae45a0651bc7de00f09d824
Signed-off-by: Saggi Mizrahi <smizrahi@redhat.com>
Reviewed-on: http://gerrit.ovirt.org/10253
Reviewed-by: Dan Kenigsberg <danken@redhat.com>
Tested-by: Dan Kenigsberg <danken@redhat.com>