Run large-ops test only on hp nodes

It turns out this is actually implemented as a performance test
with no normalization (it's manually tuned).  It only works on
hpcloud at the moment.

Joe is going to work on improving this, but for now, just run
on hpcloud so we don't lose a test.

Change-Id: Iec9162824752e11cfc4845f8c168c5c62100d185