smb/client: preserve open info type across compound queries

contains_posix_file_info describes the metadata stored in the
fi/posix_fi union. GET_REPARSE and QUERY_WSL_EA do not update that
union, so clearing the flag while processing those responses can make
POSIX metadata look like FILE_ALL_INFORMATION.

Set the flag when CREATE or a validated query response actually
populates the union, and leave it unchanged for auxiliary compound
operations. This also avoids changing the type when a query fails
before copying any metadata.

The issue can be reproduced against a Samba server with SMB3 UNIX
extensions enabled:

  mount -t cifs //<server>/<share> /mnt/cifs \
        -o vers=3.1.1,posix,reparse=nfs,actimeo=0
  mkfifo /mnt/cifs/test-fifo
  umount /mnt/cifs
  mount -t cifs //<server>/<share> /mnt/cifs \
        -o vers=3.1.1,posix,reparse=nfs,actimeo=0
  stat -c '%F %s' /mnt/cifs/test-fifo

Before this change, stat reports "fifo 1024" although the server-side
EOF is zero. After this change, it reports "fifo 0".

Fixes: 9df23801c83d ("smb311: failure to open files of length 1040 when mounting with SMB3.1.1 POSIX extensions")
Signed-off-by: Ze Tan <tanze@kylinos.cn>
Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Paulo Alcantara <pc@manguebit.org>