LU-3616 mdt: deny write on executed file during restore

LU-3616 mdt: deny write on executed file during restore

After commit c42b426c87c3d3b1dc9eda612cc831293dc80d68, from Gerrit
patch/Change-Id Ic8f82ddc9a56206307c2e5be2523fb7ce42b8638
(at http://review.whamcloud.com/3035) for LU-1338 (now HSM-5), it
is allowed to write in a file being executed during it is restored.
This patch revert to expected behavior (ETXTBSY).
Also added test_30c in sanity-hsm to verify this behavior.

Signed-off-by: Bruno Faccini <bruno.faccini@intel.com>
Change-Id: Id1e2f624dd02c2bec18ffe6cb1ae9198c1cfd23a
Reviewed-on: http://review.whamcloud.com/7636
Tested-by: Hudson
Tested-by: Maloo <whamcloud.maloo@gmail.com>
Reviewed-by: John L. Hammond <john.hammond@intel.com>
Reviewed-by: jacques-Charles Lafoucriere <jacques-charles.lafoucriere@cea.fr>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>