Updated setup_environ() to check whether /sbin/initctl is already a symlink or not before applying the initctl hack for apt-get. This avoids backing-up a symlink and destroying the real back-up in the case that setup_environ() is called multiple times without a cleanup() in between.
Add 'custom' to the custom-built OpenMPI deb package version.
NO_AFFINITY=1 is required to utilize all cores on all non cluster-compute/GPU instance types due to the shared virtualization layer not supporting processor affinity properly. However, Cluster Compute/GPU instance types use a near-bare-metal hypervisor which *does* support processor affinity. From minimal testing it appears that there is a ~20% increase in performance when using affinity on cc1/cg1 types implying NO_AFFINITY=1 should *not* be set for cluster compute/GPU AMIs.