Remove explicit locking of struct file.

• Introduce a finit() which is used to initailize the fields of struct file in such a way that the ops vector is only valid after the data, type, and flags are valid.
• Protect f_flag and f_count with atomic operations.
• Remove the global list of all files and associated accounting.
• Rewrite the unp garbage collection such that it no longer requires the global list of all files and instead uses a list of all unp sockets.
• Mark sockets in the accept queue so we don't incorrectly gc them.

Tested by: kris, pho