Chmod the socket file as read-write

If a socket file is created by a non-root user on my system, the
permissions are set to 000, as in, nobody can read or write. This change
explicitely calls chmodSync to set the file permissions to 600, which
at least allows the user to connect to the socket.

Signed-off-by: Johannes Ebke <johannes.ebke@tngtech.com>