b510116fd2
The startup code used to scan the list of unused sockets retrieved from an older process, and to close them one by one. This also required that the knowledge of the internal storage of these temporary sockets was known from outside sock.c and that the code was copy-pasted at every call place. This patch moves this into sock.c under the name sock_drop_unused_old_sockets(), and removes the xfer_sock_list definition from sock.h since the rest of the code doesn't need to know this. This cleanup is minimal and preliminary to a future fix that will need to be backported to all versions featuring FD transfers over the CLI.