Remove existing OOM test impl

Remove existing OOM test impl

The current OOM test impl is too inefficient to be used on the
large test suites. It loops running 'main' multiple times, once
for each alloc in the 'main' method. This has complexity
'n * (n + 1) / 2' in terms of total alloc count. It will be
replaced by a more efficient impl whicih runs individual test
cases instead. This will have same complexity but the values
of 'n' will be much smaller, so a net win.

Signed-off-by: Daniel P. Berrange <berrange@redhat.com>