Revert "fs: Do not check if there is a fsnotify watcher on pseudo inodes"

This reverts commit e9c15bad ("fs: Do not check if there is a
fsnotify watcher on pseudo inodes"). The commit intended to eliminate
fsnotify-related overhead for pseudo inodes but it is broken in
concept. inotify can receive events of pipe files under /proc/X/fd and
chromium relies on close and open events for sandboxing. Maxim Levitsky
reported the following

  Chromium starts as a white rectangle, shows few white rectangles that
  resemble its notifications and then crashes.

  The stdout output from chromium:

  [mlevitsk@starship ~]$chromium-freeworld
  mesa: for the   --simplifycfg-sink-common option: may only occur zero or one times!
  mesa: for the   --global-isel-abort option: may only occur zero or one times!
  [3379:3379:0628/135151.440930:ERROR:browser_switcher_service.cc(238)] XXX Init()
  ../../sandbox/linux/seccomp-bpf-helpers/sigsys_handlers.cc:**CRASHING**:seccomp-bpf failure in syscall 0072
  Received signal 11 ...