Additional SYSV init script fixes (3).

Additional SYSV init script fixes (3).

* In read_mtab(), fix problems (!?) in the mounts file. It will record
  'rpool 1' as 'rpool\0401' instead of 'rpool\00401' which seems to be the
  correct (at least as far as 'printf' is concerned). Use this using the
  external 'echo' command (and not the one built in to the shell) because
  the internal one would interpret the backslash code (incorrectly), giving
  us a \ 1 instead.
* Remove reregister_mounts() - no longer needed.
* For Gentoo, the zfs_log_failure_msg() should use eend(), not eerror()
  (which requires an error message, which we don't have).

Signed-off-by: Turbo Fredriksson <turbo@bayour.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #3488
Closes #3509
Closes #3514