LU-14629 sec: forbid file rename from enc to unencrypted dir

LU-14629 sec: forbid file rename from enc to unencrypted dir

fscrypt allows renaming an encrypted file from an encrypted directory
into an unencrypted directory. But it leaves the file encrypted,
sitting in an unencrypted directory, which can lead to unexpected
issues.
So just prevent this kind of rename, and adapt sanity-sec test_47
accordingly.

Signed-off-by: Sebastien Buisson <sbuisson@ddn.com>
Change-Id: I38e17caa4786c1c8d80a363a826a5aa298eb0980
Reviewed-on: https://review.whamcloud.com/43404
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: James Simmons <jsimmons@infradead.org>
Reviewed-by: Oleg Drokin <green@whamcloud.com>