cifs: fix reconnect with SMB1 UNIX Extensions

When mounting with the SMB1 Unix Extensions (e.g. mounts
to Samba with vers=1.0), reconnects no longer reset the
Unix Extensions (SetFSInfo SET_FILE_UNIX_BASIC) after tcon so most
operations (e.g. stat, ls, open, statfs) will fail continuously
with:
        "Operation not supported"
if the connection ever resets (e.g. due to brief network disconnect)

Cc: stable@vger.kernel.org
Reviewed-by: Paulo Alcantara (Red Hat) <pc@manguebit.com>
Signed-off-by: Steve French <stfrench@microsoft.com>