Gracefully handle long DAEMON_SOCKET_DIR path names. #4465

With this commit, all platforms will be able to handle
arbitrarily long DAEMON_SOCKET_DIR names.  Previously, they were
limited to 108 characters due to how Unix domain sockets work.

Non-Linux Unix platforms will fall back to a directory in
/tmp and Linux will start using abstract domain sockets.
Allow shared_port to fall back to local directory. #4465

In some cases, we don't actually want to use the abstract namespaces
- for example, if a client (condor_ssh_to_job) wants to register a
socket with the shared port.  Hence, we allow fallback to the
old style DAEMON_SOCKET_DIR.

On non-Linux platforms, if DAEMON_SOCKET_DIR is more than 100 chars,
then the fallback may fail.
Fixups for Windows based on batlab tests. #4465
Merge branch 'V8_3-gt4465'