instead of removing '..' in a given path, call
kern_path with LOOKUP_BENEATH flag to prevent
the out of share access.

ran various test on this:
smb2-cat-async smb://127.0.0.1/homes/../out_of_share
smb2-cat-async smb://127.0.0.1/homes/foo/../../out_of_share
smbclient //127.0.0.1/homes -c "mkdir ../foo2"
smbclient //127.0.0.1/homes -c "rename bar ../bar"

Cc: Ronnie Sahlberg <ronniesahlberg@gmail.com>
Cc: Ralph Boehme <slow@samba.org>
Tested-by: NSteve French <smfrench@gmail.com>
Tested-by: NNamjae Jeon <linkinjeon@kernel.org>
Acked-by: NNamjae Jeon <linkinjeon@kernel.org>
Signed-off-by: NHyunchul Lee <hyc.lee@gmail.com>
Signed-off-by: NSteve French <stfrench@microsoft.com>