staging: lustre: lnet: change lnet_handle_md_t to proper struct

Change lnet_handle_md_t from a typedef of another typedef into
a proper stand alone structure. Create the inline functions
LNetInvalidateMDHandle and LNetMDHandleIsInvalid to handle this
new piece of data.

Signed-off-by: James Simmons <uja.ornl@yahoo.com>
Reviewed-on: https://review.whamcloud.com/20831


Reviewed-by: Olaf Weber <olaf@sgi.com>
Reviewed-by: Doug Oucharek <doug.s.oucharek@intel.com>
Reviewed-by: Dmitry Eremin <dmitry.eremin@intel.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>