staging: lustre: llite: Remove filtering of seclabel xattr

The security.capability xattr is used to implement File
Capabilities in recent Linux versions. Capabilities are a
fine grained approach to granting executables elevated
privileges. eg. /bin/ping can have capabilities
cap_net_admin, cap_net_raw+ep instead of being setuid root.

This xattr has long been filtered out by llite, initially for
stability reasons (b15587), and later over performance
concerns as this xattr is read for every file with eg.
'ls --color'. Since LU-2869 xattr's are cached on clients,
alleviating most performance concerns.

Removing llite's filtering of the security.capability xattr
enables using Lustre as a root filesystem, which is used on
some large clusters.

Signed-off-by: Robin Humble <plaguedbypenguins@gmail.com>
Intel-bug-id: https://jira.hpdd.intel.com/browse/LU-9562
Reviewed-on: https://review.whamcloud.com/27292


Reviewed-by: John L. Hammond <john.hammond@intel.com>
Reviewed-by: Sebastien Buisson <sbuisson@ddn.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>
Signed-off-by: James Simmons <jsimmons@infradead.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>