cifsd: lookup a file with LOOKUP_FOLLOW only if 'follow symlinks = yes'

Some vfs help functions lookup a file with
LOOKUP_FOLLOW regardless of the "follow symlinks"
option.

Signed-off-by: Hyunchul Lee <hyc.lee@gmail.com>
Signed-off-by: Namjae Jeon <namjae.jeon@samsung.com>
Signed-off-by: Steve French <stfrench@microsoft.com>