LU-8249 lnet: potential deadlock in lnet

LU-8249 lnet: potential deadlock in lnet

Fixes potential deadlock in LNetMDAttach (vfree must not be called in
interrupt context in linux kernel versions prior to 3.10).

Signed-off-by: Quentin Bouget <quentin.bouget.ocre@cea.fr>
Change-Id: I1b421b470bab97d58f441040c39b9f1caf11b1fe
Reviewed-on: http://review.whamcloud.com/20676
Reviewed-by: Doug Oucharek <doug.s.oucharek@intel.com>
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: James Simmons <uja.ornl@yahoo.com>
Reviewed-by: Henri Doreau <henri.doreau@cea.fr>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>