tests: remap_dead_pid[_root] -- Run in namespace only

These tests check for file descriptor being assigned
to the pid which is freed already, so check them
in PID namespace only, otherwise the kernel may
give PID someone else and the check from
commit c4cf5f0b
might trigger and stop testing procedure.
Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
Acked-by: Tycho Andersen <tycho.andersen@canonical.com>
Signed-off-by: Pavel Emelyanov <xemul@virtuozzo.com>

test/zdtm/static/remap_dead_pid.desc

-{'flavor': 'h'}
+{'flavor': 'ns'}

test/zdtm/static/remap_dead_pid_root.desc

-{'flavor': 'h'}
+{'flavor': 'ns'}