The number of times that we have received a response
to a link test packet during the current test. This
object will start at zero when the corresponding
instance of hpicfLinkTestStatus is set to 'active'.
It will increment each time the agent receives a
response from the destination of this test. Note
that the number of failed attempts is given by
hpicfLinkTestAttempts - hpicfLinkTestSuccesses.