Added a temporary CHECK to diagnose MESOS-8687.
Added a temporary CHECK to diagnose MESOS-8687.

From the stack trace in MESOS-8687, it appears the `httpSequence`
within `ProcessBase` was null during `ProcessBase::_consume`. In
order to diagnose how this can occur, this adds a CHECK that will
print the pid and endpoint name.

dforsyth/mesos,gsantovena/mesos,reneploetz/mesos,jpeach/mesos,jpeach/mesos,asamerh4/mesos,Gilbert88/mesos,Gilbert88/mesos,andschwa/mesos,dforsyth/mesos,gsantovena/mesos,Gilbert88/mesos,abudnik/mesos,chhsia0/mesos,jpeach/mesos,jpeach/mesos,abudnik/mesos,chhsia0/mesos,gsantovena/mesos,kaysoky/mesos,abudnik/mesos,asamerh4/mesos,dforsyth/mesos,Gilbert88/mesos,kaysoky/mesos,asamerh4/mesos,asamerh4/mesos,asamerh4/mesos,kaysoky/mesos,asamerh4/mesos,gsantovena/mesos,Gilbert88/mesos,andschwa/mesos,Gilbert88/mesos,Gilbert88/mesos,chhsia0/mesos,andschwa/mesos,andschwa/mesos,reneploetz/mesos,dforsyth/mesos,reneploetz/mesos,reneploetz/mesos,dforsyth/mesos,jpeach/mesos,chhsia0/mesos,gsantovena/mesos,andschwa/mesos,abudnik/mesos,asamerh4/mesos,reneploetz/mesos,abudnik/mesos,gsantovena/mesos,reneploetz/mesos,gsantovena/mesos,reneploetz/mesos,dforsyth/mesos,dforsyth/mesos,jpeach/mesos,chhsia0/mesos,chhsia0/mesos,jpeach/mesos,abudnik/mesos,abudnik/mesos,andschwa/mesos,andschwa/mesos,kaysoky/mesos,kaysoky/mesos,kaysoky/mesos,chhsia0/mesos,kaysoky/mesos