Engine-based SSLSocket does not need AppData file descriptors

It looks like the `AppData` structure always allocates `fdsEmergency` even if it's not possible for them to be used. Eliminating the allocation of these file descriptors would be a nice clean up.

Currently it appears as though the OpenJDK JMH benchmarks can't be run on my workstation because `AppData` is allocating a ton of file descriptors too quickly. I could probably up the `ulimit` but that seems to be not addressing the underlying issue.