cli: Ping command success message need to be rephrased(#918749)

ovirt-shell ping success message needs to be rephrased.

Change-Id: I9db7fa5c022713448674f4204470a7c502a1cfe5
Bug-Url: https://bugzilla.redhat.com/show_bug.cgi?id=918749
Signed-off-by: Ravi Nori <rnori@redhat.com>