zdtm: remove extra code from file_fown

The testcase is buggy -- the signal is delivered _before_ we checkpoint
and restore it, thus it checks nothing. But after the fix test fails,
due to bug in fowners restore. Will fix it later.

Signed-off-by: Andrey Vagin <avagin@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>